"But, look here, Mr. Temple," said Jack, impulsively and with just the slightest quiver in his voice, "he's my father."

"Yes, I know, Jack," Mr. Temple said in a sympathetic tone, "and I know what you're thinking of. You're thinking your father is a prisoner and ill-treated. And you're saying to yourself that while we hold back here from appealing to the government, something dreadful may happen to him. Isn't that so?"

Jack gulped unashamedly, and turned his head away. "Something like that," he said, in a muffled voice.

The older man dropped a hand on his shoulder. "Don't worry too much, my boy," he said. "We may appeal to Washington, and let the consequences go hang, if that is the only way to bring back your father. But we don't want to act too hastily. Let's turn in now and get a good night's sleep. Then in the morning we'll decide on something definite."

It had been a long discussion, and Bob and Frank were content to do as Mr. Temple proposed. Jack, perforce, agreed, although the strain of the last few days, which he had carried alone, was beginning to tell on him and he yearned for instant action. He showed the others to their rooms, Bob and Mr. Temple sharing Mr. Hampton's room, and Frank bunking in with Jack himself.

After Frank had undressed and tumbled into bed, so dog-tired, as he said, that he could barely keep his eyes open to see the way to his pillow, Jack went out to stand in the starlight on the porch. After leaning against a pillar some minutes, during which his active brain kept milling endlessly over the details of the past few days, he had an impulse to go over to the radiophone station and talk to the guard, an ex-cowboy, on duty there since the attack by three Mexicans at the time this story opened.

Hands in his pockets, head bowed in thought, he moved across the hard packed sand, his feet making practically no sound.



CHAPTER XII

JACK DISCOVERS A TRAITOR

Two figures stood at the door of the radio station power house. The station was a duplicate of Mr. Hampton's other station on his Long Island estate, earlier described. So engrossed were the two men in whispered conversation that they were unaware of Jack's noiseless approach.

The soft sibilant sound of whispering which came to his ears just as he was about to approach the door roused Jack from his reflections. His suspicions were on the alert because of the happenings of recent days, and he halted. Certain, after standing a moment with every nerve tensed, that he had not been seen, Jack backed cautiously until again around the corner of the building.

Who were the two men? What were they whispering about? Pressing against the side of the building, Jack thought quickly. One of the two must be the night watchman. Perhaps the other was the man who kept guard at the station by day. If he were, thought Jack, then, perhaps, some new danger menaced and the night man had called the day man to help him. This theory also would account for the fact that they were whispering, instead of conversing in normal tones.

So probable did this supposition seem to Jack that he decided to join the men and ask what the danger was. Caution, however, prompted him to reconnoitre by peeping around the corner before stepping into the open. The next moment he was thankful he had done so. For, as he looked, one of the two struck a match and held it in cupped hands to a cigarette, and Jack saw the man was Remedios.

Drawing his head back quickly, Jack leaned against the building, trying to compose his thoughts. What was Remedios doing here? Not many hours before he had foiled the plan of the traitorous Mexican chauffeur to deliver him and his friends to the enemy. Was Tom, the ex-cowboy, on guard at the radio plant, a traitor? Jack could not believe it.

Footsteps were approaching from around the corner. Jack looked around wildly. There was no shelter near enough to which to flee. He whipped out his automatic, flung himself down alongside the wall, and waited.

Two men appeared, but instead of rounding the corner they moved straight ahead. They were in earnest, but low-voiced conversation. They did not see him.

Jack stifled an exclamation. The man with Remedios was Rollins, his father's trusted assistant. So stunned was Jack at the revelation that he did not strain to overhear what they were saying. In a moment they were beyond earshot.

Trembling with rage at this evidence of treachery on the part of Rollins, Jack rose to his feet. He intended to stalk the two conspirators. Then a new idea occurred to him. What were they doing at the radio plant? Perhaps, for reasons of their own, they had damaged it or put it out of commission. He decided to investigate.

Rollins and Remedios were now out of sight toward the front of the ranch house. Perhaps Rollins would have the audacity to take the other into his room, which opened like the other rooms directly upon the porch or gallery. If so, Jack could surprise them later. First, he would investigate at the radio plant.

Walking swiftly, he approached the door of the power house. An electric light shone within. The guard, Tom, jumped up from a chair where he had been sitting, reading, at the sound of Jack's hurried footsteps. His hand reached for the ready revolver at his side, but was withdrawn at sight of his visitor.

"Oh, it's you, Jack," he said, addressing him familiarly, for a warm friendship had sprung up between the two. "I thought it might be a Greaser."

"Tom," said Jack, without any preliminaries, and showing his excitement in his voice and manner, "what was Mr. Rollins doing here? Who was that with him?"

Well enough Jack knew who the stranger was. But good friend though Tom was, Jack wanted to test him. The circumstances certainly were suspicious.

"Didn't see the other feller," Tom answered. "He stayed outside. Mr. Rollins said he was an oil driller. Mr. Rollins went into the station there." Tom motioned to the radio operating room beyond a closed door. "Asked me to throw on the juice so he could use the telephone."

"Whom did he talk to?"

"Why, I don't know," said Tom. "How would I?"

"How long was he in there?"

"Why, fifteen, twenty minutes. Maybe half an hour. Why, Jack? Anything wrong?"

"Yes, Tom, there is," said Jack. "Can I trust you?"

Tom looked hurt.

"That's fer you to say."

"Excuse me, Tom," said Jack. "But after what I've just seen I don't know whom to trust. Yes, I believe you're true blue, Tom. I'll tell you. But wait a minute."

He walked to the door and looked out. The coast was clear.

"Tom," said he, returning, "I'm going to take you into my confidence. Listen."

In as few words as possible he related their adventures that day and the part played by Remedios. Then he added that in Mr. Rollins's companion he had recognized the Mexican chauffeur.

"What do you make of it?" he asked.

"Treachery," said Tom, emphatically. "But who'da thought it of Mr. Rollins?"

They looked at each other puzzled.

"I wish I knew whom he spoke to by radio and what he said," declared Jack.

"Wish I'da listened," mourned Tom.

Both stood silent. Suddenly the still night was shattered by a series of racketing explosions. Jack sprang for the door.

"Remedios's flivver," he cried to his companion. "There isn't another car in the world can cough like that."

By the time he had emerged from the radio station the car could be heard shooting away down the desert trail toward Ransome.

"Too late," said Jack, disgustedly. "He's gone. I should have surprised them together."

He thought a moment, then turned to the other.

"Listen, Tom," said he. "Not a word about all this. I think I'll not let Rollins know that I suspect him, but will talk this over first with my friends. And if he comes here to radio again listen to him, and report to me what he says."

"All right," said the big ex-cowboy. Then as a new idea occurred to him, he asked: "But how about tellin' my side pard, Dave? He's on duty days. He oughta know, too."

"I don't know Dave as well as I do you," said Jack. "Certainly he ought to be informed, so that he can be on the watch, too. Can he be trusted?"

"You can count on Dave," said Tom. "We been pardners for years. That bow-legged son o' Satan an' me been through lots o' ruckuses in our time. If there's any shootin' to be done, count us in. You know how I kin shoot."

"I ought to know," said Jack. "You taught me."

"Well, then, I'll let Dave in on the secret."

"All right," said Jack, moving away toward the house. "Good night."

He started for the ranch house, but again came back.

"Rollins mustn't know I was down here," he said.

"He won't know from me," Tom assured him.

When Jack reached the house, he found Mr. Temple, Bob and Jack on the front porch in their night-clothes. Rollins was there and had introduced himself. All four were discussing the disappearance of the flivver.

"You know how I sleep," said Bob. "But it made so much noise it waked even me."

"Where have you been, Jack?" asked Frank. "Why, you haven't undressed. I thought you turned in when I did. But I was so sleepy I never noticed when I tumbled out of bed that you weren't there."

Jack felt Mr. Rollins's eyes on him. It made him uncomfortable.

"Oh, I couldn't sleep," he said. "So I came out for a turn in the night air before going to bed."

"Where were you walking?" asked Mr. Rollins quickly.

Jack found lying distasteful, but decided it would not do in this case to tell the whole truth. Fortunately, on leaving the radio station, he had swung about in a circle, so as to approach the house from an almost opposite direction.

"Over there," said Jack, indicating the direction from which he had come. "There's a little rise some distance beyond there, but in this feeble moon-light you can't see much, so I came back. Then I heard the flivver."

"Do you think that fellow Remedios came here himself and drove it off?" asked Frank.

"He certainly had his nerve, if it was he," said Bob.

Jack noticed that while Rollins was watching him keenly Mr. Temple, who had not taken part in the conversation, was studying Rollins.

"Oh, it must have been Remedios," Jack said boldly. "Did anybody get close enough to see him? Who came out first? Did you notice, Mr. Rollins? You must have just arrived. I see you are still dressed."

"Yes, I had put my horse up in the corral," said Rollins, calmly, "and was walking over here to the house, when I heard the car. I came around to see who was calling at this late hour, but all I could see was the disappearing car. Of course, I knew nothing of your day's adventures until your friends came out, when we introduced ourselves and explanations followed."



CHAPTER XIII

THE NET IS DRAWN TIGHTER

That obvious lie on Rollins's part gave Jack the final assurance that the man was in the plot against them. Burning with indignation, he wanted to expose Rollins but with an effort of self-control he choked back the hot words and also managed to keep his anger from showing in his face.

But it was an effort. Fortunately the others came to his rescue. Frank began to shiver in his pajamas and called attention to the fact that the night air was chill.

"Yes," said Jack, glad of the change in subject, "no matter how warm the days out here, the nights are always cool. Let's go inside."

All trooped into the living room, which was dining room, too. In the big fireplace they found a wood fire laid by the thoughtful Gabby Pete, ready to be touched off in the morning. The talkative camp cook slept in the bunkhouse some distance away, in the opposite direction from the radio plant. While the others dragged blankets from their beds and returned to the living room, wrapped up in them like Indians, Jack touched a match to the wood and the fire soon was blazing merrily.

Rollins would have excused himself on the plea of fatigue after a long day's ride, but Mr. Temple halted him.

"So long as we are here altogether," he said, "it won't hurt matters, and may help them, to have a little talk."

From his chair in front of the fire, Mr. Temple looked up inquiringly at Rollins, who stood to one side of the fireplace, his face in the shadows. The latter did not speak. Jack thought quickly. Was it wise for Mr. Temple, unaware of Rollins's duplicity, to discuss matters with him? He decided not. He was bending down to throw more wood on the fire and without rising he interposed an objection.

"Mr. Rollins must be pretty tired," he said, glad his face was averted because he feared the scorn in his eyes would betray him. "And we've all had a hard day. Suppose we let the discussion go until tomorrow."

Rollins spoke precipitately, and Jack believed there was a little note of relief in his voice.

"Yes," said he, "that would be better. I am pretty tired, as Jack says. Well, I'll turn in. Good night. I'll see you at breakfast and after that we can have our talk."

Shaking hands with Mr. Temple and throwing curt nods to Bob and Frank, Rollins left the room. A moment later Jack arose and followed swiftly but silently to the door on the gallery. Peering around the doorpost cautiously, he assured himself Rollins had entered his own room, then returned.

The others looked at him in surprise, unable to understand the meaning of his actions. Jack soon enlightened them.

Crouched before the fire and with his eyes on the door for signs of interruption, while the others pulled their chairs close about him, Jack in a low voice outlined his experiences of the night.

When he spoke of Rollins's using the radio, Frank uttered an exclamation.

"That's how the enemy learned just what time we would arrive," he declared.

Jack shook his head.

"No," said he. "All Rollins had to do to spread that information was to tell Remedios. The latter could notify the men who laid for us."

"Well, then, whom was he telephoning to?"

Jack again arose and moved to the door and peered out. No signs of life. He returned and resuming his position said in a low voice:

"That's what I've been asking myself. I've thought it over and I believe I've found the answer. Either he was radioing to the Calomares ranch in Old Mexico where father probably is held a prisoner, or else he was sending a message to the fellows who stole our airplane."

Bob, the belligerent growled in his throat.

"The big stiff," he muttered. "I'll go get him now and we'll choke it out of him."

He half rose from his chair, but his father pushed him back.

"Don't blame you, Bob," said Jack, grinning. "It's what I wanted to do myself. But I believe there is more to be gained by watching Rollins—at least until we have more to go on."

"Probably," said Frank, "if we put it up to him now, he'd be able to lie out of it."

"But he couldn't lie out of being seen with Remedios," said Bob. "Or of using the radio."

"Frank is right, though," declared Jack. "Rollins would frame some alibi, and all we'd succeed in doing would be to put him on his guard."

Mr. Temple had been thinking deeply. Now he interrupted.

"Jack is probably correct in his surmise as to who Rollins was calling by radio," he said. "Probably this Calomares ranch is headquarters for the Mexican rebels who are making trouble for us. If it was the ranch that Rollins called, he may have been making his report on today's proceedings. But if he was calling the airplane, that is a more serious matter. It may mean trouble for us tonight, perhaps another attack."

"Great guns," grumbled Bob, "don't these birds ever sleep? Well, believe me, if the Heinie that stole my airplane comes around where I can get my hands on him, I'll fix him."

"You wouldn't hurt him, Bob, would you?" said Jack.

"Huh." That was all Bob replied. It was enough.

"I wouldn't do a thing to him, either," said Frank. "Except I'd turn his Kaiser mustaches down so hard they'd never point up again."

Bob and Frank, joint owners of the airplane, grinned at each other.

"Well, fellows," said Jack, "We have got to sleep. So I propose that we stand guard turn about tonight. It's pretty late now, midnight or thereabouts, so that if we stand two hour watches, the three of us, we'll pull through nicely without spoiling Mr. Temple's slumber."

The older man protested he was as able to stand a watch as any of them, but the boys wouldn't have it so. Finally it was agreed that Jack should take the first watch of two hours, Bob would succeed him and Frank would have the last watch. The man keeping watch would sit inside his bedroom door opening on to the gallery, with Jack's revolver. As the bedrooms adjoined, while that of Rollins was the last in the house, it would be easy enough to guard both.

The night passed, however, without incident.

It had been agreed beforehand that after the expiration of Frank's watch at 6 o'clock there would be no necessity for keeping further watch. Gabby Pete would be up and busy at his early morning tasks, and the oil drillers housed in the bunkhouse also would be stirring about. Therefore, after barring the door, a precaution Bob also had taken in the room shared with his father, he turned in without awaking Jack.

Worn out by their trip of the day before with its attack and the excitement of the night, all slept soundly, and Gabby Pete did not get them up. It was almost 10 o'clock when Jack awoke. He called the others, and soon all were dressed and ready for what the day would bring forth.

Jack was the first dressed. He found Gabby Pete in the kitchen, peeling potatoes, and asked if they could have breakfast.

"Sure thing," said Gabby Pete. "Have it fur you right away. Nice fresh aigs an' ham an' coffee. How's that?"

"Fine. Have you seen Mr. Rollins this morning?"

"Yeah. Give him breakfast early. He lef word he hadda go over to Number Two well where they're still drillin' an' hain't struck oil yet, but said as how he'd be back later today. He tuk them two drillers from the bunkhouse with him."

"Did you know Remedios sneaked up last night and took his flivver again, right from under our noses?" Jack inquired.

"No, that so?" Gabby Pete dropped his paring knife and potatoes in surprise.

"Well, he did," said Jack, starting to leave.

Gabby Pete jumped up, almost upsetting his pan in his haste, and called to Jack to wait. Wiping his wet hands on a big blue apron that looked incongruous on the old cowman, he pulled open a drawer in a kitchen table and took out a flat blue envelope which he handed to Jack.

"Almost forgot this," he said. "Your tellin' me about that there scoundrel of a Greaser put everything else out o' my mind. Must be gittin old an' forgetful. One o' these days I'll forgit my head."

He would have rambled on garrulously, but Jack interrupted. He turned the envelope over curiously. It bore no address or writing of any kind, and was sealed.

"What's this for, Pete?" Jack inquired.

"Oh, that's somethin' Mr. Rollins musta dropped out o' his pocket at breakfast. Found it on the floor beside his chair after he was gone. Will you give it to him?"

"All right."

Jack returned to join his companions.

"Have we any right to open this?" he said, after explaining how he had obtained the envelope. "I for one believe that we should. It may contain valuable information to us."

"You're right, Jack," said Mr. Temple. "I'm a partner in this oil enterprise, and if one of our trusted employees is a scoundrel we are entitled to know it. Give me the envelope. I'll take the responsibility."

While the others looked on, Mr. Temple ran a knife along the edge and slit the envelope open. Inside was a mass of documents and a letter. Mr. Temple unfolded them, gave one look, then with an exclamation jumped to his feet.

"Great Scott, boys," he cried. "This is important. Luck is certainly with us."



CHAPTER XIV

THE KEY TO THE MYSTERY

"What is it?" cried Jack, pressing forward.

"Yes, tell us," demanded Bob and Frank as in one breath.

The three boys crowded around Mr. Temple, who in one hand held the mass of documents and in the other the letter. He was reading the latter.

"Boys," said he, "this proves Rollins's complicity in a plot against us. But it makes matters more puzzling and complicated, too."

"How is that, sir?" Jack inquired.

"Well, first of all," said Mr. Temple, holding up the thick sheaf of papers, "this is Mr. Hampton's own original list of the leases secured by the group of independent oil operators to which I belong and which he represents here in the field."

"Is it a copy of the list I recovered from the thief who stole it from Mr. Hampton's house on Long Island?" asked Bob.

"No," smiled Mr. Temple. "It is the original. That was the copy. And this letter with it is one written by Rollins to a man in New York City who is one of the minor officials of the Oil Trust. It is too long to read to you. But from it I gather that Rollins is a spy in the employ of this official."

"Say, Dad," declared Bob, "this is too much for me. If the Octopus is responsible for our troubles, then where do the Mexicans come in? And vice versa?"

"That's what I had in mind, Bob, when I said this discovery complicated matters," said Mr. Temple.

"Sh," warned Jack, from the window toward which he was glancing at that moment. He sprang forward to see better. "Here comes Mr. Rollins now. And in a tearing hurry, too."

Rollins jumped from his horse and ran along the porch to his room. They heard the door slam, and then sounds of a furious searching being carried on. The boys and Mr. Temple, gathered around the door and window, looked at each other significantly.

"Found he dropped his papers and came back for them," whispered Frank.

A moment later Rollins called for Gabby Pete from the door of his room. The cook hurried to him from the kitchen.

"Pete, did I drop an envelope—a long blue envelope—at breakfast?" asked Rollins, making no attempt to conceal his anxiety.

Before Gabby Pete could reply, Jack stepped impulsively from the doorway.

"Yes, you did," said he. "Pete gave it to me to keep for you."

"Where is it?" Rollins brusquely demanded.

"Step into my room," said Jack.

Rollins complied. When he saw Mr. Temple, Bob and Frank, he recoiled as if to flee. But Jack barred the doorway. Rollins was speechless. Mr. Temple advanced, holding out the document and the letter.

"Your duplicity is discovered, Rollins," he said. "I make no apology for having opened your sealed envelope, because last night Jack Hampton discovered you at the radio station with Remedios, and we knew you were faithless to your trust. Come, make a clean breast of it."

Rollins's face went white.

"You, you read the letter?" he gasped.

Mr. Temple merely nodded.

Rollins seemed to shrink and grow older before their eyes. Suddenly he sank into a chair. His shoulders sagged. Pressing his hands to his eyes, he bent forward and began to cry. Not the noisy crying of a child but great, dry, wrenching sobs.

"Come on, fellows," said Jack in a low voice. "Let's leave him to Mr. Temple."

The older man nodded approval and the three boys filed out, closing the door behind them. Simultaneously each drew a long breath of relief. Bob was the first to speak.

"Dad'll get it out of him," he said

"I'm hungry," said Frank plaintively.

At that moment, Gabby Pete poked his head from the doorway of the kitchen. Seeing the boys, he called:

"Come an' git it."

The three started on the run for the dining room, their youthful spirits rebounding from the depressing scene in the room they had just quit in answer to the tang of a perfect day and the cook's breakfast call. Bob suddenly halted with an exclamation.

"How about Dad?"

"Oh, he's too busy to miss his breakfast," said Frank. "Anyhow, we can get the cook to put up something for him."

"Yes, I'll speak to Pete about it," said Jack. "Come on."

They ate hungrily with little conversation. Pete hovered near and his presence restrained them from talking about the topic that was uppermost in their minds.

"How about taking a look at the radio plant?" asked Jack when they had ended breakfast.

The others agreed eagerly. They were in the act of leaving the table when Mr. Temple appeared. They crowded about him with questions.

"Easy, easy there," he protested. "I'm hungry as a hunter. Suppose you boys wait outside for me while I get a bite, and then I'll join you."

When Mr. Temple emerged, he lighted a cigar and leaned against a pillar. The boys stood about him. For several moments he was silent, staring out over the expanse of desert to the hills beyond, all shimmering beneath the heat of the summer sun.

"It's a long story," he began, "but I'll simplify it for you. Rollins held the key to the mystery. He has a family back East, an invalid wife, a son in college, a daughter just preparing to enter college. All that takes money, for doctor bills and school bills and clothes for the girl. Rollins was a poor man on a salary.

"He needed money and couldn't see his way to getting it. Then a minor official of the Octopus put temptation in his way by making him a proposition. Mind you, he wasn't one of the big men of the Oil Trust. I feel certain they know nothing about all this.

"This man proposed that Rollins obtain certain inside information about the independent oil operators and sell it to him. Rollins wanted to, but couldn't get the information. It was too closely guarded by Mr. Hampton.

"It was then that another temptation came Rollins's way." Mr. Temple paused. "A weak man seems to carry certain earmarks that draw scoundrels to him, boys," he said. "It was so with Rollins. At this moment a representative of Calomares, the Mexican landowner who is backing the northern rebels, sought him out with a proposition that he betray his employers. The rebels, as I suspected, wanted to make trouble for President Obregon, of Mexico, by embroiling him with the United States. And the way they wanted to set about it was by raiding the independent oil operators. They needed a spy at our headquarters, and they proposed that Rollins should become their man.

"Then Rollins had an inspiration. He told the Mexicans that if they would help him, he would aid them. It was agreed. The agent who had acted for Calomares in the negotiations was this German, Von Arnheim, an aviator and a German secret agent in Mexico during the war. He took the man Morales with him to Mr. Hampton's Long Island home to steal the duplicate list of independent leases and other data which Rollins had learned was kept there."

"That's where I came in," grinned Bob.

"Yes," said his father, "and it was because you foiled them that Rollins came into possession of Mr. Hampton's own original copy of the list and other data. For he stole it from Mr. Hampton's effects after Von Arnheim and Morales had carried him away captive in our airplane."

"How about this attack on us yesterday?" asked Jack.

"As you suspected, it was for the purpose of capturing me, too," said Mr. Temple. "And Rollins had let the bandits know when I would arrive. Remedios was his go-between."

"Well," said Jack, "there's only one thing more."

"What is that?" asked Frank.

"Why, I'd like to know whom Rollins radioed to last night."

"I found that out, too," said Mr. Temple. "He was talking to the Calomares ranch in Old Mexico, which has a very powerful station, according to Rollins. He says the German, Von Arnheim, told him that there are similar powerful radio stations scattered throughout Mexico and South America, all built by German money for the use of its spy system. And he said this German told him the most powerful station of all was on an island in the Caribbean, and that it was so powerful it could communicate with Nauen, Germany."

It was apparent that Mr. Temple had concluded his explanation, and Bob and Frank began to ply him with questions. Jack, however, stood silent, his face averted. Mr. Temple presently broke from the others and laying a hand on Jack's shoulder whirled him about.

"Father?" asked he, in a kindly tone.

"Yes, sir."

"Well, Jack, I've got the beginnings of a plan in mind. But first I must get more information from Rollins. Then I'll talk to you again."

Jack looked him squarely in the face.

"Mr. Temple," said he firmly, "I'm desperate. Father is everything in the world to me. I'll wait to talk with you. But I tell you frankly the only plan that appeals to me is to ride into Old Mexico and rescue him."

The eyes of Bob and Frank, who had turned to listen, lighted up, and they nodded vigorous approval. Mr. Temple stood off and looked at the trio of husky fellows as if seeing them for the first time.

"Perhaps," said he, "that is what you will soon be doing."



CHAPTER XV

TO THE RESCUE

"I may be wrong," said Mr. Temple, thoughtfully, "in giving my sanction to this plan to rescue Mr. Hampton. But I do not believe so. And, all things considered, it seems the best if not the only way out.

"I have been accustomed to regard you as mere boys, but the conduct of every one of you in our adventures lately shows me you are able to think and act for yourselves. Yet I don't know. Jack, you and Frank are motherless. But—if anything happened to Bob—his mother never would forgive me."

"Say, Dad, forget it," grumbled the big fellow to hide his emotion. "I can take care of myself."

His father's eyes lighted approvingly as they surveyed his truly heroic frame.

"Yes, I guess you can," he said. "And you carry a cool head, too. At any rate, I've given my approval."

He smiled whimsically, then looked from one to another of the three eager young fellows.

"My daughter Delia was right," he said. "When I left home she said I was wrong to think of you any more as youngsters, and that the first thing I knew you would be making use of your wit and ingenuity to take care of me. And now her words in a measure are coming true."

All four were grouped around the dining room table. For several hours plans for the rescue of Mr. Hampton had been discussed and rejected. Out of it had grown a plan which called for a daring invasion of the enemy's territory by the boys.

Mr. Temple had impressed upon them the necessity for preventing the United States government from being involved in the situation. He had explained a number of angles not made clear before. Among other considerations, he said, was the fact that practically all the Central and South American republics were jealous of their big Yankee neighbor.

"If our government were to make a hostile move toward Mexico," he declared, "the other Latin republics would misconstrue our motives. They would consider that because of our size we were acting the part of the bully in order to reap financial benefit. They call us the 'Dollar Republic,' you know. Our interests in Central and South America would suffer a severe setback."

Accordingly, it was distinctly up to the boys and Mr. Temple to effect Mr. Hampton's rescue themselves. And out of the discussion had grown the plan to have Jack, Bob and Frank make their way to the Calomares ranch and offer their services to the rebel forces in the guise of young Americans who were seeking adventure.

Once within the rebel stronghold they would bide their time and await an opportunity to free Mr. Hampton and escape with him.

"I, for one, won't be content until I get back our airplane," said Frank, when the details were being discussed. "Probably we shall be able to recapture it, and then we can all four make our escape in it. The 'plane carries three easily and can be made to carry four at a pinch."

"Hurray for you," cried Jack, delightedly. "That's a real idea."

"I'll say so," declared Bob. "We can do it, too. I know we can."

Carried away by the boys' enthusiasm, Mr. Temple nodded approval.

Jack said he was certain enlistment in the rebel forces would offer no difficulties. From Tom Bodine, the guard at the radio plant, with whom he had had many conversations during the past two months about conditions on the border, he had learned that adventurous young Americans fought frequently on one side or another in the Mexican revolutions.

"I can speak Spanish pretty well, too," Jack pointed out. "And Bob and Frank have a smattering of the language, which they picked up from me."

It was true. Two years before Jack had spent his summer vacation in Peru where his father was engaged at the time in inspecting mining properties. Jack had learned considerable Spanish during his stay and on his return home had continued his studies of the language. Moreover, he had aroused the interest of his chums to such an extent that they also had begun to study Spanish. Often, when by themselves, the three boys spoke to each other in the language. Spanish, by the way, is the easiest of all foreign tongues to learn, as, unlike French and Italian, all letters are sounded, and the grammar is very simple.

Mr. Temple was not to accompany the boys because, in the first place, his age and distinguished appearance would arouse suspicion. Young fellows riding in to enlist in the rebel forces was something that could be understood. But in his case it would be a different matter.

He would stay at the ranch with Rollins, whom he decided to give another chance. Rollins knew the business details of the oil operations and unless he were retained the work could not go on. For that reason, and also because he believed Rollins was truly repentant for his treachery and would be faithful in the future, Mr. Temple retained him.

Rollins had supplied valuable information for the expedition. He gave the exact location of the Calomares ranch, in a valley amid low mountains more than one hundred miles to the south.

There were two possibilities that the boys might be recognized for what they were: if Remedios should arrive at rebel headquarters, or if Von Arnheim or Morales recognized Bob as the youth who had foiled them on Long Island. Neither was very likely. Remedios, they learned from Rollins, had no intention of leaving the district because even if the boys tried to cause his arrest he had a mysterious political pull with the American officials, practically all of whom were of Mexican descent. As for Morales and Von Arnheim they had had only a fleeting glimpse of Bob and he could disguise his appearance sufficiently to make that of no account.

"Well, boys," said Mr. Temple finally, "if we all were back in New York under normal conditions I should consider this just about the craziest notion ever, and never would consent to your carrying it out. But out here, amid these changed surroundings, it seems the natural thing to do. For the life of me I can't bring myself to feel any alarm."

"That's right, Dad," said Bob. "Don't you worry. We'll be all right."

It was now late afternoon. Tom Bodine was to escort the boys to the border as soon as darkness fell, making a big swing around Ransome, so as to avoid notice, and set them on their way. They would travel by horseback, all three having ridden since childhood. There were a number of good mounts in the corral from which to select.

The boys planned to ride the major portion of the night until they should reach a cave in the first of the Mexican foothills, where they would spend the next day in hiding. Tom Bodine knew the cave of old and was able to give the boys the location of certain landmarks which would make it easy for them to find it. The following night they would continue their journey, and this should bring them to the Calomares ranch on the morning of the second day.

"Time to get ready," said Mr. Temple, looking at his watch. "And, remember, the very first thing you must try to do is to get into their radio station and call me. Day or night, the men here will be watching for your signal and will call me. I'll be mighty anxious about you. So remember."

"We shall call you, sir," said Jack, as the boys moved away. "And don't worry. I'm sure we'll come out all right."



CHAPTER XVI

A SOUND IN THE SKY

"Good-bye, Tom."

"S'long, Jack."

"Keep a watch for our signal. We'll call you."

"I will that. An' if it's in trouble you are, Dave an' me'll be ridin' just as fast as we can to help you. Wish you'd let me go 'long. I'm half minded to follow you."

"No, no. We'll stand our best chance alone. They won't suspect we're other than a bunch of wild young fellows out for adventure."

Tom grumbled, but the force of the reasoning was apparent to him. They leaned from their horses for a last firm handclasp, then Jack rode on to join Bob and Frank who sat on their horses some distance ahead.

"You're the boy to give it to 'em, Jack," called the big ex-cowboy in a last farewell. "Give 'em thunder."

Jack waved a parting salute as he joined his comrades. Frank and Bob did likewise. Then with night settling down over the vast desert waste they rode on into old Mexico.

Beside the white stone marking the international boundary, Tom Bodine sat his horse like a statue. Moodily he watched until they were out of sight. It was a hard life Tom had led in his day and when he took the job at the radio plant it was with a sigh of relief at the ease ahead of him. But now despite his fifty years, the last thirty of which had been filled with hard knocks, he felt the old call to adventure urging him on.

With drooping head, he turned his horse toward home. But hardly had the animal started forward, than he dragged it about again.

"Let's go," he shouted to the empty silence, and whirling his sombrero aloft, brought it down on his horse's flank. Then he rode on after the three figures that had been swallowed up in the darkness.

Far ahead of him, for Tom had taken considerable time to reach his decision, rode the three companions. The young moon shed only a wan and wraithlike radiance over the plain. They were alone, and the parting with their last friend, combined with the solitude of the open spaces, had its effect upon them. They rode awhile in subdued silence. But not for long. Frank's lively spirits were the first to rebound.

"Race you to that rock," he cried, pointing to a solitary outcropping of rock, about twice a man's height, about a quarter of a mile ahead.

"You're on," cried Jack, spurring his horse.

"Attaboy," yelled Bob, doing likewise.

With a shout that shattered the silence as if a band of wild Indians were hitting the trail, the three boys dashed away.

Presently they pulled up by the rock, practically neck and neck. Their eyes were alight now with the zest of adventure.

"Gee, it's great to be alive," cried Frank.

"You said it," declared Bob.

Jack nodded laughingly, but the next moment his face became grave.

"Just the same," he said, "we mustn't do that again."

"Why not?" demanded Bob.

"Well, for one thing, we must save our horses as much as possible. We already have come twenty miles, and we have thirty miles more to go before reaching Tom's cave."

"For one thing?" questioned Bob. "What's your other reason?"

"Just that we don't want to draw attention to ourselves."

"You're right, Jack," said Frank. "I'll not start anything again."

They jogged on.

A martial trio they made. Jack was clothed in the khaki shirt, riding breeches, high laced leather boots and sombrero in which he had met the boys on their arrival at Ransome. Bob and Frank were similarly outfitted. Tom Bodine was about of Bob's proportions, and his partner Dave Morningstar had the build of the slighter Frank. These two old cow punchers had given the boys the run of their wardrobes. Each lad carried an automatic at his hip swinging from a well-filled cartridge belt. In addition, Jack bore his repeating rifle in a leather scabbard on his saddle.

Frank cast an appraising eye over himself and his comrades, and grinned with approval. Despite Jack's rebuke, he could not long keep silence.

"Well, here we go, fellows," he said cheerfully, "just like the Three Musketeers. Jack with your air of melancholy you can be Athos. Bob is big enough to be Porthos, although I have got his appetite. I'm Aramis."

"Aramis was always dreaming about the ladies," said Bob slily. "Heard from Della lately?"

Frank was silent a moment under the sly dig, his thoughts flying back to the faraway Long Island home. But his irrepressible spirits would not permit him to remain silent for long, and soon he burst forth again.

"All we need to make it complete," he said, "is D'Artagnan. I wonder if we'll find him."

Jack made no answer. His thoughts were busy turning over plans for the rescue of his father. Bob, too, was unusually silent, thinking of the parting from his own father and the latter's anxiety which almost had prevented his making this venture. Frank pursed his lips to whistle, thought better of it, and jogged along as silent as his companions.

So they rode hour after hour, only the creak of leather, the occasional stumble of a horse or the distant call of a coyote breaking the stillness. At length a low range of foothills, upflung before them, began to take shape out of the darkness with their near approach. Presently Jack called a halt.

"Somewhere in there," said he, "lies Tom's cave."

It was in the early hours before dawn, when the darkness if anything becomes more intense. A chill nipping wind long since had caused the boys to unroll the rubber ponchos strapped to the back of their saddles, and drape them over their shoulders. As they stood now in the eerie darkness, striving vainly to locate the landmarks of tree and rock which Tom had given them, the howl of a hunting coyote floated down the wind. The sensitive Frank shivered.

"That sends the gooseflesh up my spine," he said.

"Are you scared?" asked Bob.

"I'm scared stiff," averred Frank. "My hair is standing up so straight I wonder how my sombrero stays on."

"Me, too," said Bob.

"Liar," said Frank.

"You're another," said Bob. "You're not scared. I know you too well."

They grinned affectionately at each other. Jack who meantime had been investigating, turned with a worried expression.

"I've followed Tom's directions faithfully," he said. "He said to lay our course south by south-west and showed me what he meant on my compass. I haven't deviated a hair's breadth. Somewhere about here should be the first landmark—three rocks shaped like a camel lying down. But I can't see them."

"Nothing to worry about in that," said Frank. "Probably we haven't gone far enough. Let's push on."

"That must be it," said Jack with relief. "Well, come on."

Before they could get into motion, however, Bob uttered a warning whisper.

"Listen," he said. "I heard a horse stumble behind us on the trail."

They listened breathlessly a moment, but no further sound was heard.

"Keep your guns handy," whispered Jack. Whenever the three were together he took command. "Don't fire without cause, however," he whispered. "If there is someone behind us, it may be another traveller."

Again came the sound of a horse stumbling. All heard it distinctly. Jack peered into the darkness and called firmly:

"Who are you?"

"Challenge him in Spanish, why don't you?" muttered Frank.

Before Jack could repeat his challenge, however, a familiar voice replied:

"That you, Jack? This is Tom."

"Tom? Tom Bodine?"

"The same," replied the ex-cowboy, materializing out of the darkness, and approaching. "And glad I am," he added, "to find you."

"But, good gracious, Tom, is anything the matter? Why are you here? I thought we left you heading back for home five hours ago?"

"No, you just left me," said Tom. "That's all. I didn't head home, because I wanted to come along. Been a-trailin' you all the way. And here I am."

Jack was surprised, indeed. But now that Tom was with them, he experienced a sense of relief. To venture into a strange land without a guide, and in pitch darkness, besides, was a pretty stiff undertaking. The responsibility of looking after his friends was no light one.

"To tell the truth, Tom," Jack said, "I'm glad you came."

Bob and Frank echoed his words heartily.

"I had just about decided when you came up," Jack added, "that I had lost my way. Frank thought, however, we merely hadn't gone far enough to find your landmarks."

"He was right," said Tom. "You come straight as a die. All we got to do is to ride on a piece an' we'll be in the snuggest cave ever you see."

Riding two abreast, Tom and Jack in the lead and Frank and Bob close behind, they pressed on another twenty minutes when Tom called a halt to indicate a clump of rocks close at hand which suggested in their outline a crouching camel. Then he led the way toward the left.

"Wait, wait," called Bob, in a tense voice that reached the ears of all, and caused them to halt. "Keep your horses quiet and listen. There. I was right."

All sat silent, and distinctly there came to their ears the hum of an approaching airplane.



CHAPTER XVII

INSIDE THE CAVE

"What is it?" whispered Tom Bodine, to whom the sound was unfamiliar. "Sounds like machinery of some kind."

"It's an airplane," Jack answered.

"Airplane? An airplane?" said Bob, low voiced. "It's better than that. It's our airplane, if I know anything."

"Righto, Bob," agreed Frank. "I'd know the old baby's voice a mile off."

"They've shut off the motor," said Jack. "They must be going to land. But where in the world could they land in these hills and in this darkness, too?"

Tom Bodine slapped his knee.

"That's it," he said emphatically. "That must be it."

"What?" asked Jack.

"Why, there's a big level place just below the cave I was tellin' you 'bout. A plateau. Smooth as a floor."

The hum of the airplane had died away. The boys and their guide never had caught sight of the machine in the darkness.

Suddenly Frank pointed in the direction whence the sound of the airplane had come, ahead and slightly to the left.

"I thought I saw a light there," he whispered. "It was just a faint streak of orange. Now it's gone."

"Look here," said Bob to Tom Bodine, "does that cave face this way or is it on the other side of a hill?"

"It's on t'other side," answered Tom, "an' near the top."

"Well, I'll bet you there's somebody in that cave. And the light that Frank saw was some kind of a signal to the airplane."

The big ex-cowboy scratched his head.

"Mebbe you're right," he said doubtfully. "I don't know 'bout such things. But who'da thought that cave would be discovered. Why, I just come on it accidental like onct when I was wanderin' through these hills."

"Boys, there's only one thing to do," said Jack in a determined voice, "and that's to investigate."

"Righto, Jack," said Frank eagerly. "Here's our chance to get back our airplane."

"You said it," declared Bob. "Let's go."

"Not so fast," said Jack. "First we must have a plan of campaign. Tom, what's the lay of the land? How far away is the cave? Would it be better to leave our horses here and approach on foot?"

"Cave's not more'n half a mile from here," answered Tom. "It's just around the shoulder o' this hill we're on right now and near the top. I tole you 'bout that big rock in front o' the entrance an' them three lonesome trees at the foot that give you a bee-line to the rock. Well, we can git to them trees without bein' noticed an' tie our horses there an' then sneak up afoot."

"Is there only the one entrance to the cave?"

"Only one," answered Tom. "There's a kind o' chimney up through the rock to the top o' the hill. But nobody couldn't git out there in much of a hurry. We won't have to worry 'bout that."

Frank had an idea.

"How far would those fellows in the airplane have to go to reach the cave after landing?"

"Oh, le's see. 'Bout as fur as us, I reckon."

"Maybe we can cut them off before they enter the cave," said Frank. "They'll be busy about the airplane for several minutes before they start to make their way to the cave. How would they have to approach the cave?"

"Same way as us from the trees on," said Tom.

"Well, if we hurry," Frank declared excitedly, "maybe we can capture them before they reach the cave."

"Right you are, young feller," approved Tom. "But we'll have to leave our horses behind or they might give us away. We can't tie 'em to those trees like we planned."

"We can't hobble them," said Jack, thinking quickly, "because they would wander aside a little distance, anyway. And we may want them again in a hurry."

"Tell you what," said Tom, "seems like I remember a clump o' trees just this side o' them three I spoke about. We can tie 'em there. An' them fellers in the machine won't have no horses, so ours ain't likely to nicker."

"Good," said Jack. "You lead the way and we'll follow."

Presently at a low-spoken word from the guide the boys dismounted and tied up their horses. Then, Jack carrying his rifle, and the others following close at his heels, revolvers in hand, they pressed on toward the three trees forming Tom Bodine's landmark.

As they reached the trees, low exclamations burst from the boys. Hitherto, they had been cut off from the plateau by the shoulder of the hill. Now it lay below and before them. This of itself would not have permitted them to see, as the darkness was intense. But now the scene was illuminated by a number of oil flares stuck upright in the ground in a rude circle.

And right in the middle of the circle was the airplane stolen from Bob and Frank. There could be no mistaking the all-metal body nor the peculiar wing spread, even at that distance of close to half a mile.

Several figures were moving about. As the boys looked on, these seized oil flares and started moving toward them.

"Here's where our turn comes at last," said Frank.

Jack laid a hand on his arm.

"Better than that, Frank," he said. "How many do you make out?"

"Three is my guess."

"The two men in the airplane and the man in charge of the cave," said Jack. "Dollars to doughnuts, the cave is undefended right this minute. What do you say to capturing it and laying for them there?"

All four were grouped together, and consequently all heard Jack's proposal. Bob and Tom Bodine agreed eagerly.

"Lead the way, then, Tom," said Jack, "because you know the route. And be quick."

Swiftly, yet withal cautiously, because the cave might be defended, they approached the big rock. As they sidled around it, a gleam of light from the mouth of the cave at the rear of the rock fell athwart their path. Involuntarily they drew back.

Then Jack brushed Tom Bodine aside and took the lead. His repeater thrust before him, crouching, he entered the mouth of the cave. A moment later his whisper came back:

"Coast's clear."

But the others already were at his heels.

A hasty glance around revealed the first of the two chambers, which Tom had said the cave possessed, was luxuriously furnished and lighted by a powerful electric bulb enclosed in a huge frosted globe suspended from the middle of the roof. There was no time for further investigation because Jack already was pushing on toward the heavy hangings at the rear covering the mouth of the second chamber, and the others clung to his heels.

Parting the hangings quickly, Jack threw his rifle to his shoulder. Then he and his companions received their second big surprise. The room was empty of human occupants. But it, too, was brilliantly lighted.

And it was a radio broadcasting station.

To the trained eyes of the boys that much was apparent at first glance. In one corner of the tremendous cave hummed the dynamo. From it, of course, came also the electricity for the lights. Before they could pursue their investigations, however, Tom Bodine, who had dropped back to the outer entrance, issued a warning hiss. Then he darted across the outer room and joined them.

"Three of 'em," he whispered. "They'll be here in a minute."

"Good," said Jack, taking command. "We'll give them a surprise. These hangings are fastened to rings on a big pole up above us there, and they'll slide easily. Tom, you and Bob grab the hangings in the middle and be ready to pull them aside when I say the word. Frank, you and I will stand here in the middle and keep them covered."

All took their assigned positions as the sound of voices was heard at the outer entrance. Jack peered between the two folds of the hangings and smiled with satisfaction.

"Let's go," he said.

The hangings flew aside.



CHAPTER XVIII

THE FIGHT IN THE CAVE

"Hands up, gentlemen," ordered Jack, rifle to shoulder.

"And be quick about it," added Frank, revolver extended.

Tom and Bob, the hangings disposed of, ranged themselves on either side of the pair. Four weapons covered the group in the outer room.

The three men, who had advanced well to the center of the room, stared dumbfounded at these apparitions. Then amazement gave place to anger, and one of the trio made a move as if to draw his revolver.

"None of that," commanded Jack, sternly. "Up with them quick or I'll shoot."

Three pairs of hands were unwillingly elevated. Two of the men wore sheepskin jackets and leather helmets and the boys surmised correctly that they had been up in the airplane. Bob felt certain they were Morales and Von Arnheim, the two who had made the trip to the East to steal Mr. Hampton's papers and whom he had foiled in that purpose, but who had succeeded in stealing the airplane and making their way to Mexico in it. The other was a rangy man of about twenty-six, keen and shrewd-looking, and had the appearance of an American. Evidently he was the guardian of the cave. And it was he who had moved to draw his weapon when surprised. A tough customer and one to be watched, thought the boys.

"Face about," ordered Jack.

They obeyed.

"Keep them covered, Tom," Jack then commanded. "Well search them."

With weapons held ready, the three boys advanced. At that moment, the caretaker of the cave took one step forward and instantly the lights in both rooms faded out and the cave was in inky darkness.

He had pressed a button in the floor, switching off the lights.

The boys were so taken by surprise that for a moment they did not fire. Neither did Tom, for fear of hitting them as they were in front of him. This gave their three enemies an opportunity to shift position and fling themselves prone.

When after their surprise, the boys did fire, their bullets merely pinged against the distant wall and did no damage. But the flash of their weapons betrayed their positions and answering bullets came uncomfortably close. One swept Jack's hat from his head.

From behind them Tom Bodine's revolver spoke, as the enemy thus betrayed themselves. The soft thud of a bullet striking flesh, a groan, choked off in the middle, a hasty scrambling to get away from the danger point on the part of the man struck, then silence.

This silence was so profound the boys seemed to hear the beating of their own hearts, and tried to hold their breath for fear of betrayal. They had thrown themselves prone after the first volley and lay so close they were touching, Jack in the middle.

Each side was fearful now of firing at the other, lest the flashes give their position and an answering bullet find its mark.

Jack thought quickly. Putting his lips to the ear of each of his companions in turn, he whispered:

"Wait till I get Tom and come back. Then we'll make our way to the entrance."

Each signified by the pressure of a hand that he understood. Certainly it would not do to have the enemy escape and thus cut them off in the cave!

Slowly, carefully, noiselessly, Jack wormed his way to the rear and when he considered he must be in Tom Bodine's neighborhood he began whispering in a tone that could not be heard more than three feet away:

"Tom. Tom. Tom."

A hand gripped his leg. A voice whispered so low it was barely audible to him:

"That you, Jack?"

"Yes. Listen."

Running a hand over Tom Bodine's body, Jack found his ear and, as he had done with Bob and Frank, set his lips to it. He explained his purpose to gain the entrance to the cave and prevent being bottled up. Tom nodded approval, and Jack was about to return to his companions when he suddenly thought of the radio room beyond, and its possibilities. It would never do to leave that unguarded. Their enemies could telephone the Calomares ranch. Then, even if the boys escaped, their identities would have become known at rebel headquarters. Their chances of rescuing Mr. Hampton would go glimmering.

Once more Jack set his lips to Tom's ear and explained the situation.

"That's right," whispered Tom in return. "Tell you what. I'll guard this here inner room from behind the rocks in this doorway. You three stop up the outer entrance, an' well have 'em bottled."

Jack made his way back to his comrades, and the three started crawling. They moved inch by inch, so as to avoid bumping into furniture—a number of heavy chairs had been seen standing about the great room.

Jack was in the lead, Frank at his heels, Bob bringing up the rear. Cautiously, tortuously, they made their way ahead for what seemed like ages, pausing frequently to listen.

After one such pause, as he again started to follow Frank, Bob felt a form brush against him from the side. Then an arm shot out and encircled his neck. Bob wriggled about to face his opponent and threw both arms about him in a mighty clasp.

As they fell to the floor, Bob heard a strangled cry from Frank and a grunt from Jack. They, too, had come to grips with the enemy. Their three opponents had started for the door with the same purpose held by the boys—that of bottling up the other side. The two crawling trios had brushed against each other in the middle of the floor.

Now three individual fights raged furiously on the floor of the cave in Stygian darkness. Every man fought for his very life. The sob of labored breathing was the only sound—that and the threshing about of bodies.

Tom Bodine was sick with rage at his helplessness, for he dared not shoot lest he hit one of the boys, and he could not see to take a hand. He decided to try to find that button in the middle of the floor of the outer cave which the enemy had used to throw off the lights. If not that, perhaps there was a wall switch somewhere. In his pockets was a box of safety matches. With these in his hands he started for what he thought was the middle of the room.

Recklessly Tom struck and lighted matches, searching the floor for that button, stopping after each match burned down to his fingers to listen to the panting, heaving struggle going on about him.

At last he found the button and pressed it. Light once more flooded both caves, dazzling to the eye after the pitch darkness of the moment before. Jack and Frank were still tightly locked with their respective foemen. But at the very moment the lights were switched on, Bob got the upper hand of his man with a famous hold he had used to advantage in winning his wrestling fame at school. There was a heave, and then Bob straightened up and the other went hurtling through the air. He was the American of the enemy trio.

The man fell on his left side, a yard or more away, by a quick twist avoiding the descent on his head, which is the usual result of such a wrestling toss. His right arm was outflung and, as he skidded along the floor, the fingers of his right hand came in contact with a revolver dropped by one of the wrestlers.

Twisting about like a cat, with a convulsive movement, the man came to his knees and fired. There was a warning shout to Bob from Tom Bodine. But the man's aim was far from steady, and the shot went wide.

Bob leaped forward as if shot from a catapult, letting out a wild yell as he did so. It was a tremendous leap from a standing position, and he descended feet first on the other before he could discharge the revolver again. Beneath the impact of Bob's weight the man went down like a shot rabbit and lay still. Bob disarmed him, turned him on his face, pulled his arms behind him and began tying them with his belt.

Meantime Jack was getting the better of his man, the Mexican. But Frank, slightest of the three boys, was putting up a losing fight against the German. The latter had him down and was kneeling on his chest with his hands throttling the boy. Frank's face was purple and the breath was whistling in his throat, while his efforts to throw the other off were becoming more and more feeble.

Tom Bodine took in the situation and sprang forward, clubbing his revolver. He brought it down on the German's head. There was a sickening thud. One blow was enough. The German's hands relaxed their grip on Frank's throat, and he rolled over unconscious.

At the same moment Jack pinioned the arms of the Mexican, and the latter lay helpless.

The fight was over.



CHAPTER XIX

RESTING UP

Swiftly Tom Bodine trussed up the unconscious German with the man's own belt, while Jack similarly treated the thoroughly cowed Mexican, Morales. Meanwhile, Bob went to Frank's aid, assisting him to a chair, bringing him water from a spring in a corner of the inner cave and fanning him with his sombrero.

None of the three boys had suffered more serious injuries than bruises, but Frank had been badly battered in the encounter with his heavier opponent and the muscles of his left shoulder had been severely strained.

Despite the mauling he had received, Frank wanted to go and inspect his beloved airplane at once and Bob, the co-owner with him, was equally eager. Jack, however, protested.

"No, sir," said he firmly, "you are in no condition to go chasing off down this rocky slope. The airplane isn't going to fly away. It's in a pocket in the hills that nobody is going to discover. And, anyhow, there is nobody around in this desert place to do any discovering.

"Moreover," he continued, "it is almost morning now. We all have been riding all night and with this fight coming on top of everything else, we are thoroughly tired out. So, instead of any more conversation tonight, I propose that we turn in and go to sleep, leaving one man on guard. At the end of two hours he can call another fellow, and in that way we can all get four or five hours sleep. I'll take the first watch and—"

At that moment a groan from one of the prisoners on the other side of the room interrupted, and with an exclamation Bob started forward.

"Good gracious," he said, "I'd forgotten all about that chap. His arm felt wet and sticky when we were wrestling and I believe he's the man Tom wounded with that first shot in the darkness."

Bending over his late opponent, Bob noted a dark brown stain on the left shoulder of his coat.

"Only a flesh wound, I reckon," said the other. "But it sure hurts. Are you going to leave me like this?"

Bob flushed.

"Of course not," he said. "What do you think I am? Here, let me help you up and we'll have a look at it."

Bob assisted the other to a chair. His hands were then untied, the coat sleeve cut away and an examination made of his injury. It proved not serious. The man told Bob where to find a bottle of iodine. He winced under the sting of its application, but made no outcry. Then a rough bandage was made of clean handkerchiefs, and the boys stood back to examine their handiwork, for all had taken part in the operation.

"You're some fighter, kid," the other said approvingly to Bob. "But I reckon I'da got you at that if it hadn't been for that arm."

"Maybe so," Bob modestly agreed. "You put up a stiff fight."

"You're an American, aren't you?" asked Frank. "What's your name? And how do you happen to be with these fellows?"

"Why not?" said the other, answering the last question first. "I'm a rolling stone and joined up with this outfit because it looked like something doing. And that's what I want. As for my name, it's Roy Stone. And you guessed right. I am an American. Born an' raised in Wooster, out in Ohio."

He paused and looked curiously from one to the other of the boys. Tom Bodine was examining the two other prisoners for possible injuries needing attention. Stone nodded toward him.

"I can place a fellow like that, all right," he said. "Know this kind down here on the border. But who are you? You're only kids. What's your game? Are you with Obregon?"

"No, indeed," said Bob. Turning to Jack, he whispered:

"Is it safe to tell him who we are? He's an American. And, somehow, I have an idea he might help us."

"Well, it won't hurt, I guess," said Jack, doubtfully. "He might escape and betray us to rebel headquarters, but I suspect we can guard against that. Besides, he's bound to find out our identities, because those other two chaps will recognize you."

"Hardly in this rig," said Bob, referring to his clothing. "We talked all that over, you remember."

"That's right. I had forgotten."

Bob and Jack had drawn aside during the whispered colloquy. Now Bob turned back to his prisoner.

"Look here," he said. "We'll have a little talk later. Right now we all need a good sleep."

Without more ado, Bob and Frank tied Stone's hands and led him to his bed, behind a curtain in one corner of the outer room. They considered that inasmuch as he was wounded, he was entitled to the bed. The German had recovered consciousness from the blow on the head dealt him by Tom, and the latter already had ranged him and the Mexican along the wall where the sentinel could keep an eye on them. For themselves, the boys pulled a heavy rug to another portion of the wall, spread the heavy hangings formerly covering the door to the inner cave on top, and here Bob and Frank lay down with their ponchos over them. Presently they were joined by Jack who had planned to mount guard the first two hours, but who had been overruled by Tom Bodine.

"No, you don't," said the latter. "I'm a tougher bird than you, and I take this job myself, an' that goes."

Too tired to protest very vehemently, Jack turned in after exacting a promise that Tom would call him at the end of two hours. The old cowman, however, had no such intention. It was not until eight hours later that he summoned Jack. The lights in the cave still burned brightly, for Tom had refrained from switching them off for the obvious reason that they made it easy to keep an eye on the prisoners. Day-light, however, showed at the mouth of the cave. When Jack noted the time, he began to scold.

"Forgit it," said Tom Bodine, gruffly. "You boys needed a good sleep while I'm an old hand at ridin' night herd. It didn't bother me none to stay up."

Without further words, he turned in and was asleep almost on the instant. Jack roused Bob and Frank, and while Bob mounted guard at the mouth of the cave where he could keep watch both on their prisoners and on the approach from below, the two others explored a rude pantry behind a curtain. They found a plentiful stock of provisions, which made it unnecessary for them to draw upon their own limited food supplies for breakfast.

When they themselves had eaten, they released the captives one at a time and fed them, afterwards replacing their bonds. The Mexican and the German were surly and uncommunicative. The latter tried to ply them with questions, but when they refused to answer he adopted a bullying tone and threatened them with all sorts of dire punishment. His threats, however, were no more effective at breaking down their silence than were his questions.

Bob remained at the doorway to avoid the risk of recognition by Morales and Von Arnheim as the youth who had foiled their attempt to steal Mr. Hampton's papers from his Long Island home. Jack, who had no means of knowing how much the traitor, Rollins, might have told Von Arnheim in the past about Mr. Hampton's personal affairs, watched keenly for some indication on the German's part that he had formed an idea as to their identity, but none was forthcoming.

Jack was correspondingly elated.

"I suppose," he said to Frank, after Morales and Von Arnheim had been fed and returned to the other side of the cave, "that Rollins never bothered to speak about us because we were just boys. Then, too, you fellows arrived only the very day that we discovered Rollins's treachery and put a stop to his communications with these people."

"That may all be true," said Frank. "Probably it is. Just the same, Von Arnheim and Morales are bound to put two and two together and make a shrewd guess as to our identities, even if they say nothing to us about the matter.

"But," he added, confidently, "what if they do? We have them prisoners now and if we keep them well guarded until we have rescued your father, what does it matter how much they know?"

Jack nodded agreement.

"We'll have to keep mighty strict watch, though," he said. "Well, now let's feed this American, Stone. I'll draw straws with you to see who keeps guard while Bob comes to get his breakfast at the same time. He wants to talk to Stone, he said."



CHAPTER XX

CONFERRING BY RADIO

Bob, however, told his companions he had decided not to interview Stone for the time being, and explained his reason, as well as what he hoped to gain from conversation with the prisoner.

"I believe," he declared, "that Stone is a warm-hearted, adventurous young fellow with no particular love for the Mexican rebels, but merely serving under their banner for the excitement. And I believe if we approach him right we can win his help in rescuing Mr. Hampton. He must know a good deal about this Calomares ranch and if we can get him to give us some pointers it will be worth while.

"That was what I had in mind last night. But mounting guard here this morning I had time to think it over, and I decided we had better go slow and, if possible, get the advice of my father on the matter."

"But how could you do that?" asked Frank. "Go back to Hampton ranch again?"

Jack interrupted excitedly.

"No, Frank, don't you see!" he said. "Bob is thinking of the radio here in the cave. Aren't you, Bob? I'm a simpleton not to have thought of it before."

"Well," said Bob, "we've all been so excited, that's not to be wondered at. But while I mounted guard here during your breakfast, I had a chance to calm down and do some thinking."

Bob was eager to use the radio telephone at once, but Jack persuaded him to eat breakfast first. The big fellow literally bolted his bacon, bread and coffee, and then accompanied by Jack, while Frank mounted guard, he retired to the inner room where the radio outfit was located.

"Let's have a look around here before we try to telephone," said Jack. "It will take us only a few minutes. And we ought to know what we have captured. What say?"

"Fair enough," Bob agreed.

A cursory inspection quickly convinced Jack that the station was not of recent installation, but had been put in about the year 1918. Much of the equipment, while of the best at the time it was put in, had been antiquated since by improved parts.

It was a complete two-way installation, however, comprising a generator of practically sustained waves, a good control system to modulate the output, and a ground system for radiating a portion of the modulated energy as well as a receiver and a good amplifier.

"Here is this chimney in the rock about which Tom spoke," Jack pointed out. "They have hooked up through this. And the antenna, I suppose, is on top of the rock above us.

"This arc," he continued, advancing to the coils, "looks pretty strong and seems to have a rather elaborate water-cooling system. I think it is of foreign design, probably German. The Germans were early in the field with radio telephony development, you know."

"All right," said Bob, who was beginning to grow impatient, "I'll take your word for it. But what I want to know is, can we telephone my father at your ranch?"

"Say, Bob, I'm sorry," Jack said quickly. "You know how crazy Dad and I are over this radio telephone. But, of course, you are anxious to get your father. Come on, let's try. I'll throw on the generator."

Suiting action to words, Jack shortly had the generator at work, while Bob began calling through the air for his father.

"Be careful to use our code," Jack warned him. "You know Rollins said these fellows had a powerful radio station at the Calomares ranch, and if they were to pick up your call and listen in there'd be trouble."

"Right," said Bob. "But if Dave answers the signal, I'll have to ask for father, because Dave doesn't understand the code."

It was Dave Morningstar who answered, the other ex-cowboy employed as mechanic and guard at Mr. Hampton's radio plant in New Mexico. And when he had tuned to the proper pitch to hear distinctly and Bob's voice greeted him he was so surprised he stuttered and was incapable for a moment of coherent speech. Then he began to pour a flood of questions at Bob, wanting to know where he was, how he happened to be able to radio, what had happened to the boys, why Tom Bodine, his partner, had failed to return, and so on. But Bob cut him short.

"Stop it, Dave," he said. "We may be overheard. Call father to the telephone, so I can speak in code. Then I'll explain."

Fortunately, although it was past noon, Mr. Temple was at hand. So anxious was he about the boys that he had been unable to sleep during the night. All morning, despite the belief that it was folly to expect to hear from the lads so early, he had stayed at the radio plant. Now, when he heard his son's voice, there was heartfelt thanksgiving in his reply.

"Is it really you, Bob?" he asked, speaking in code. "I must have been insane to let you three lads go off on such a foolish venture. I have been tortured with anxiety every minute since you left. Tell me where you are and what has happened. And how in the world is it possible for you to radio? Are you all right?"

"Yes, we're all right, Dad," answered Bob, and there was a good deal of emotion in his voice, too. The big fellow and his father were real pals. "Don't you worry, Dad," he added. "We're doing well, thank you."

Then he retailed their adventures from the time of crossing the border into Old Mexico and leaving Tom Bodine at the boundary. There were many interruptions from his father.

"Thank heaven," said the latter, when learning that Tom Bodine had followed the boys and joined them. "He's a trustworthy chap, and to know that he is with you makes me breathe more easily."

When he came to relate the fight in the cave, Bob diplomatically made little of it. He felt there was nothing to be gained by unnecessarily harrowing the feelings of his father. The latter's anxiety, however, was great and he pumped rapid questions at his son which Bob could not avoid answering. The result was that Mr. Temple gained a fairly accurate idea of the peril in which the boys had been involved.

"But, Dad," Bob interrupted his parent's horrified exclamations, "it's all over now. None of us is injured, and we have got back our airplane."

"I know, Bob, I know," answered the older man. "But you can't understand a father's feelings. And it isn't all over yet by any means, for you haven't rescued Mr. Hampton. And you don't know what difficulties you will encounter in doing so, and what dangers you will run."

"Oh, I believe the worst is over, Dad," answered Bob. "We have captured Morales and Von Arnheim, and they were our two worst dangers. If we had encountered them at rebel headquarters and they had recognized me, our goose would have been cooked. We would have been taken prisoners, too. But now there will be nobody to recognize us. The rebels will take us for what we pretend to be, young Americans seeking adventure and riding in to enlist."

"Perhaps, Bob," said his father, only half convinced. "But let me think this over. There ought to be some other way to rescue Mr. Hampton now that you have the airplane again. Also you have these prisoners. It may be that you can gain some valuable information from them. Have you questioned them yet?"

"That's just what I was coming to, Dad," said Bob.

Thereupon he proceeded to tell his father of Roy Stone, the young American in charge of the radio plant in the cave, whom they had made prisoner. A lengthy conversation ensued. Mr. Temple was reluctant at first to have the boys reveal their identities inasmuch as so far they had escaped detection. But he saw that if an ally could be made of Stone it would be of the highest importance to the boys. He finally authorized Bob to promise Stone a suitable reward, if he thought that would appeal to him. Then, enjoining Bob to take no further steps without first consulting him by radio, Mr. Temple concluded the conversation.

To Jack and Frank, speaking in low tones at the entrance to the cave where Frank kept guard, Bob explained the gist of his conversation with his father. Tom Bodine still slumbered heavily. Stone lay napping on his bed. Morales and Von Arnheim sat with drooping heads in the heavy chairs where, while Bob telephoned, Jack had thought it best to bind them.

"Well, let's talk with Stone and see what he has to say," Jack said. "Frank and I have been talking the situation over, too, and we've got all sorts of ideas. For one thing, we thought there was a chance the rebels could be persuaded to exchange father for Von Arnheim and Morales. Stone might know how important those two worthies are considered by the rebels."

"Can't I listen in on this confab?" Frank asked, plaintively. "Or must I continue to mount guard here? Besides, I want to go down and look at our airplane, and pat it even if I can't get in and fly. I can see it from here, and it looks tempting."

"You'll have to wait awhile to do that, I expect," said Jack with a smile. "We must decide what to do next before we spend any time playing."

At that moment, Tom Bodine yawned prodigiously and sat up on his make-shift couch.

"At least I can have a voice in the conference," said Frank. "If Tom's awake he can mount guard."

"All right, fine," said Jack. "We'll leave him out here with Morales and Von Arnheim, as soon as he has had something to eat. Then the three of us can take Stone into the other room and have a talk with him."

So it was arranged.



CHAPTER XXI

GAINING AN ALLY

Before mounting guard, however, Tom thought of their horses, a detail which the boys had forgotten in the quick march of events. He and Bob descended the slope, brought the animals into the valley where there was grass along the bed of a little stream trickling from a spring, and a few trees that provided shade. The horses were hobbled to prevent wandering too far, and then left to do as they pleased. They pleased, every one, to lie down at once and roll.

Upon their return to the cave, after Bob first had inspected the airplane and found it in tiptop condition and stocked with gas and oil, Tom mounted guard while the boys carried out their intention of taking Stone into the inner room for a conference.

Stone made matters easy for all concerned by speaking first, as soon as they all were out of earshot of Morales and Von Arnheim, and telling the boys he had guessed their identities.

"Of course, I don't know your names," he said, "but I reckon one of you is the son of that American bigbug old Calomares is holding prisoner up at his ranch. And the rest of you are his pals."

Bob's face fell. He had believed their identities were unsuspected. If this man could draw so clever a deduction, then their two other prisoners could do likewise. Moreover, if they carried out their original plan and went to rebel headquarters to enlist, would they not there, too, be suspected?

"Do the others guess who we are?" he asked.

"Don't know," said Stone. "I haven't been given much chance to talk to 'em, have I? But that German is smart, and he may suspect. But"—and with this statement he set at rest a part of Bob's fears—"my bed is pretty close to this room an' I have pretty good ears. I overheard some things that Morales and Von Arnheim couldn't hear, especially when you used the radio to call your father. Anyhow, I thought it was your father. Mostly you spoke in code, but I heard you call him 'Dad' a couple of times."

The three chums looked at each other, nonplussed. Stone laughed.

"Until I made out who you were," he said, "I thought you were some wild-eyed kids looking for adventure an' comin' to the right place to find it. But once I got a suspicion, it was easy to figure out the rest. You see, I knew about your owning the airplane that Von Arnheim stole, an' about your radio stations. When you started the generator that showed me you knew something about radio, an' that was another clue.

"So I just put two an' two together. Anyhow, it finally came to me who you were. Am I right?"

"Yes," said Jack, taking the initiative as Stone concluded, "you are correct. It is my father who is held prisoner by the Mexicans, and these are my chums."

Jack regarded the other searchingly.

"We're in trouble," he said, simply, "and we need help that you could give us. How closely are you tied up with the rebels? You're an American and we are Americans. Does that mean anything to you?"

"Yes, kid, it does," said Stone. Despite the fact that he was only seven or eight years older than the three chums, he had led a roving life that had given him a world of experience and an older viewpoint, and he persisted in regarding them as youngsters. "I'm strong for the good old U.S.A.," he continued.

"But don't get me wrong. These are fine people down here, and don't you believe they ain't. Their standards aren't American standards either in manners or politics. But, just the same, they're good folks, and don't you let anybody tell you different. I wouldn't turn against them for anything. So, although your fathers have lots of money"—here he looked fixedly at Bob, who felt uncomfortable remembering his father's authorization to offer Stone money to help them—"well, don't offer me any, that's all."

Bob was silent, but Jack again stepped into the breach.

"Good for you," he said warmly. "I'm glad to hear you talk that way. But"—and here Jack paused impressively—"suppose the imprisonment of my father threatened the peace and prosperity of the 'good old U.S.A.' as you call it. What then?"

Stone looked troubled.

"See here," he said. "What are you driving at?"

"Shall we tell him what Mr. Temple says is behind all this?" Jack asked his companions.

Bob and Frank nodded agreement.

"Well," began Jack, "it's this way." Thereupon he proceeded to relate Mr. Temple's theory that the attacks on the independent oil operators, the capturing of Mr. Hampton and the attempt engineered by Rollins and Remedios to capture himself, were all part of a plan to embroil the United States government with President Obregon, as the responsible head of the country whence the outrages originated.

"And Mr. Temple says," concluded Jack, "that if the two countries did come to war, it would hurt us very much with all Latin-America."

"Sure would," agreed Stone thoughtfully. "I've knocked about among these Spanish-American republics for years, an' they all look on the little old U.S.A. as a dollar-chaser and a bully." He was silent for a moment, and when he resumed, he said: "Look here. What you've just told me makes a big difference. You haven't said yet what you are out to do. But I can make a pretty good guess. You're going to try to rescue your father without letting the American authorities know anything about it. Am I right?"

Jack nodded.

"Well, I'll help you," said Stone. "I know where he is and how to get him, an' I'll tell you all I know."

"Hurray," yelled Frank, the impulsive.

Jack and Bob contented themselves with grasping Stone's hand warmly. Realizing Stone still was bound, Bob pulled out a pocket knife and started to cut his bonds, but Stone made him desist.

"Keep this dark from Von Arnheim and Morales," he said. "And keep me tied up. They may suspect I'm throwing in with you, but I don't want 'em to know. I want to be able to make a getaway, because these parts won't be very pleasant for me hereafter."

"That's right," said Bob. "Well, even if you won't take money, you'll have to let my father or Mr. Hampton help you in some way, with a job or something."

Stone smiled tolerantly.

"Buddy," said he, "getting along is the least of my troubles."

With Stone's aid won, the boys now set about learning from him how matters stood at the Calomares ranch.

For hours they continued to talk, so absorbed that they did not realize the flight of time until Tom Bodine came to inform them the sun was near setting and to ask what they intended to do that night. By then, however, they had obtained from Stone all the information he could give them, which was considerable; Bob had had another talk by radio with his father, and a plan for further proceedings had been worked out.

Jack and Bob were to make the attempt at the rescue of Mr. Hampton alone. They were to fly to the Calomares ranch in the airplane with Bob at the wheel, as Jack was not so experienced a flyer. Bob, on the other hand, knew his machine thoroughly, and was familiar with its every trick, a knowledge much to be desired as airplanes even more than motor cars and ships develop temperament and have got to be "humored," so to speak.

Frank rebelled at the part assigned him. He was to stay behind at the cave with Tom Bodine and Roy Stone, guarding the prisoners, Morales and Von Arnheim. When they had rescued Mr. Hampton, Jack and Bob would take him in the airplane and start flying to the Hampton ranch.

By means of the radio in the airplane, which could send 150 to 200 miles, although it could receive messages from a much greater distance, the Hamptons and Bob would notify the party left behind in the cave. Then Frank, Tom Bodine and Stone would ride for the border on horseback. Morales and Von Arnheim would be left bound so as to prevent their giving an alarm or offering any interference with the programme. After the party had been given time to make its way well along toward the border, rebel headquarters was to be notified by radio from the Hampton ranch of the location of the prisoners. The latter would, therefore, suffer nothing but inconvenience.

"But what fun do I get out of this?" lamented Frank, enviously regarding Bob and Jack. "You fellows get all the fun and all the glory. I ride tamely back to the ranch."

"It is hard luck, Frank," said Bob. "But your shoulder is sore and aching from your fight last night, and I'm in better condition to operate the plane. Besides, you know we can't take you, as the plane will hold only three and when we get Mr. Hampton we'll have our full complement. Some one of us has to stay behind. You've had your share of the fun so far, anyhow, and your turn will come again."

"I don't see it," said Frank. "It looks to me as if when you rescue Mr. Hampton the fun will all be over. But that's the way with you big bullies. Always picking on the little fellow."

"Well, you see," said Bob mischievously, "I've got to keep you out of danger for Della's sake. Ouch! Wow! Letup. Can't you take a joke."

For, lame shoulder notwithstanding, Frank leaped and, bowling the big fellow out of his chair, got astride of his writhing body and began to pummel him.



CHAPTER XXII

FLYING TO THE RESCUE

"Come on. Strip."

It was Bob talking, and the command was addressed to Morales and Von Arnheim. Tom Bodine stood guard over them with leveled revolver.

"But, why?" protested Von Arnheim.

"Ask us no questions an' we'll tell you no lies," said Tom, waving his weapon. "Jest do what you're tole."

Sullenly the two men obeyed. When their outer clothing had been removed, and they stood revealed in light-weight undergarments—a well set-up powerful pair of men, about the height of Jack and Bob although neither was so sturdy as the latter—Bob halted them.

"That's enough," he said. "Here put these around you."

And he tossed them rubber ponchos which they threw around their shoulders.

Scooping up the discarded clothing of the two men, Bob and Jack retired to the radio room. Stripping quickly, Jack dressed in Morales' clothing and Bob in that of the German aviator. This arrangement was adopted because Jack could speak Spanish with considerable fluency and thus fitted into the role of the Mexican. Bob, on the other hand, was better adapted to pass as the German who, they had been informed by Roy Stone, spoke Spanish only awkwardly.

"Buenos dios, Senor," said Jack, bowing gracefully.

"Ach du lieber Augustine," answered Bob, standing at salute.

They burst into hearty laughter, in which they were joined by Frank and Roy Stone, who were present at the transformation.

"How will we do?" asked Jack.

Stone eyed them critically.

"To fellows that know Morales and Von Arnheim only by sight," he said, "you will pass for them easily enough. Both of them are smooth-shaven, which is unusual, for Mexicans and Germans both favor mustaches. But that's all the better for you boys.

"One thing you want to remember," he said to Bob, "and that is to walk pretty stiffly like you had a bone in your leg an' swallowed a ramrod. That's the way Von Arnheim always steps out, An' both of you keep your hats pulled down."

"Now you boys have got the bearings I gave you. You can easy enough find the landing field, even in the darkness. It's a big meadow as flat as a table, with the ranch house and outbuildings in a clump at one end, an' the radio station with its big tower supporting the antenna at t'other. Both places will be all lighted up, for Calomares lives like one o' them old-time barons an' he's always got so many men around the place he needn't fear nobody, so why put out lights? He likes light. He's a bug on it, in fact."

"Suits me," said Bob. "That gives me some beacons to go by."

From the foregoing it will be seen that the boys had changed materially their original plan of riding in as adventure-seeking American youths to enlist in the rebel forces, and wait their chance to effect the rescue of Mr. Hampton. As matters now stood. Bob and Jack were to land in the airplane, and while Bob stayed by it, Jack was to make his way to the room where his father was held prisoner, free him, and guide him back to the airplane, when they would fly for the border.

Of course, the plan would not be so easy of execution as it sounded. To find the ranch and make a safe landing would be a fairly easy task. The ranch was not more than fifty miles distant by air line, and in that sparsely habited country there would be no other similar group of lights to puzzle Bob. Once they had alighted, however, the difficulties would be encountered.

At first the boys had considered the advisability of waiting until a late hour to make their attempt. Rebel headquarters then would have retired for the night, and they would run less danger of encountering anybody on landing. In that event, however, they soon realized, ranch and radio station alike would be dark and Bob would have no beacons to guide him to a landing.

No, there was only one thing to do, and that was to arrive at an early hour. Moreover, there would be this advantage attached, namely, that sentries would be lax and that, with many persons coming and going in and about the ranch, the passage of a familiar figure, such as they would take Jack to be, would arouse no comment. Jack might be halted, of course, by some one desirous of conversation. But he could make some excuse to pass on. As a matter of fact he planned to wrap a handkerchief about his jaw and pretend to be suffering from toothache. This would serve the double purpose of partially hiding his features, and of excusing him from indulging in extended speech.

"All right," said Jack, finally, as he finished donning his disguise by clapping Morales' hat on his head. "Let's go."

"Ya, ya," said Bob, doing a goosestep. Once more they all had a good laugh. Then Bob and Jack walked into the outer room of the cave, followed by Frank and Roy Stone. Stone had thrown caution to the winds, and had decided not to try any longer to hide his defection from Morales and Von Arnheim.