The American shrugged his shoulders as he took the bills, rolled them up nonchalantly and placed them in his trousers pocket.

"You can find me at the Hidalgo Hotel whenever you want me," he said, "and now I must be going."

He arose from his seat, and as he did so, Donald caught sight of his face. It was the mountebank, Strong, but in his stylish clothing Don had failed to recognize him.

"Great Scott!" he muttered to himself, "the plot thickens!"

"What's that?" queried the lieutenant, who caught the muttered exclamation.

"Nothing much," replied Donald as the three men walked toward a door in the farther end of the room and he was enabled to speak without being heard, "only that is the man I'm looking for. Let's get out of the window and see if we can't head him off."

He closed the door and turned the key which he had quietly taken from the other side.

The windows were open and they looked out. They were on the side of the house overlooking a good-sized lawn.

"That's the reason they are not barred," explained Donald. "Had they been front windows, we might as well have been in jail. You go first and I'll cover the retreat."

Lieut. Grimes sprang into the window and lowered himself to the ground, just as a hand turned the knob.

"Good-bye!" muttered Donald. "Sorry I can't wait to receive you," and he followed the lieutenant.

On the ground they could hear the men trying to open the door and as they sped across the lawn toward a high brick wall, the door gave way with a crash and they could hear surprised voices.

"They have discovered our wreckage!" cried Donald. "Over the wall you go!"

"You first this time," said the lieutenant.

"No, you first. I can boost you up, but I couldn't pull you. You can pull me."

The argument was good and the lieutenant acted upon it.

A minute later he was on top of the wall.

"Great Caesar!" he exclaimed. "There's nothing under me but water."

"Never mind that," was the response. "Haul me up."

The lieutenant leaned down and gave the lad a hand.

"Here we are," he said a minute later. "We can't jump in, for there is no knowing where we are."

"Sure," from Donald. "Let's run along the wall."

This they did for about a hundred yards and then the wall ended abruptly against what appeared to be an abutment.

"We must act quickly," declared Donald. "They think you are Funston and won't hurt you. Keep up the deception. I'm going to swim for it. I'll have help here just as quick as I can. So long," and, throwing off his coat, he jumped into the water some twenty feet below.



CHAPTER XXVII.

THE ADMIRAL TO THE RESCUE.

When Donald struck the water he allowed himself to go clear to the bottom, as he wanted to find out just about how deep it was.

It was, as he had expected, about the depth of the water in the harbor and he made up his mind that he could not be far from some of the wharves that constitute the water front.

When he came to the surface, he struck out away from the wall, and by the light of the moon was soon able to see the vessels in the offing. He could also see that he was well north of the principal docks.

"I guess I'll land at the first place that offers," he thought, "and find my way to headquarters from there."

He struck out lustily, but had not been swimming more than a couple of minutes, when he heard the sharp exhaust of a gasoline launch.

Realizing that it must be an American craft, he shouted at the top of his voice.

At first there was no response, but as the boat came nearer and he shouted even more loudly, a friendly hail came over the waters.

"Where are you?" came the voice as the boat came to a stop.

"Here, to your port side," he replied.

The launch was started again slowly and Donald was soon able to make himself visible.

"Who are you?" was the first question pumped at him by the officer in command.

"Special messenger for Gen. Funston," was the response.

"Where is your uniform?"

"I'm not a soldier. I am a civilian."

"A likely story," snapped the officer, who chanced to be an ensign.

"I can't help how likely it is," snapped Donald in return. "It's true, and I want to be put ashore as quickly as possible. I have an important message and the safety of one of his staff is involved. There is also a plot on foot to capture the general himself."

"Nonsense! And besides, I can't put you ashore. I am carrying a message to Admiral Fletcher."

"But my business is important," insisted Donald.

"So is mine," declared the ensign.

He ordered his launch full speed ahead in the direction of the flagship.

"It's pretty tough," commented Donald, "but I'll prove I am right when I get to the ship."

"I hope so," was the reply. "I haven't anything against you and you may be telling the truth, but I can't take any chances."

Fifteen minutes later they drew up beside the flagship.

"Up you go," said the ensign, motioning Donald up the ladder. "I'll present you to the officer of the deck," which he quickly did.

"Here's a man I picked up in the water, sir, who says he has a message for Gen. Funston, but I had no time to put him ashore."

"Looks more like a boy than a man," replied the officer. Then to Donald: "What's this about you having a message for Gen. Funston?"

Donald repeated what he had told the ensign.

"What's that?" asked another officer, coming forward out of the shadow of the after turret.

The first officer saluted.

"Tell the Admiral your story, my lad," he said.

Again Donald repeated his story, this time going more into detail.

"Come with me," ordered the Admiral, and he led the way to the wireless operator.

"Get into communication with Gen. Funston at once," was the admiral's order.

"Here he is, sir," was the report a couple of minutes later.

"Ask him if he has three American boys on a special mission."

The answer came back promptly that he had.

"Ask him if Lieut. Grimes is missing."

Again came back the answer that he was.

"Tell the general that we have one of the lads on the Arkansas, and that he has had a strange adventure. Tell him I will send the lad ashore immediately."

"Thank you, sir," said Donald. "I knew some one would know what to do."

"You're a brave lad," was the Admiral's comment, "and I shall be glad to hear the end of the adventure. You and your companions must come out and dine with us as soon as your mission is ended."

Donald thanked him for his kindness and hastened to the launch which was to take him back.

Twenty minutes later he stood before Gen. Funston.

"You seem to have been in the water," was the general's first words.

"Yes, sir," laughed Donald. "I jumped from a wall north of town, leaving Lieut. Grimes on top of it."

"What! Lieut. Grimes on top of a wall? How did he get there?"

"He was kidnapped, sir! It was a case of mistaken identity!"

"Mistaken identity! I don't understand!"

"They took him for you, sir, because his beard is trimmed like yours."

The general smiled grimly.

"Think I shall have all my staff officers do the same," he commented. Then more seriously: "Can you lead us to the house?"

"I'm not sure about the house; but I can take you to the stone wall from which I jumped. That ought to guide us to the house."

"Right," said the general.

He called another member of his staff and gave a few brief orders.

In another ten minutes two launches loaded with regulars and armed with a rapid-fire gun in each, steamed swiftly up the harbor.

"There's the wall!" exclaimed Donald a few minutes later, "and there's where I jumped," pointing to a spot near the abutment.

The officer in command headed the boats for the shore.

"It is not only a question of freeing Lieut. Grimes," said the officer, "but we also want to capture the conspirators. This is a much more serious matter than Gen. Funston is willing to admit."

"Then if you will take my suggestion, sir," said Donald modestly, "I would let a few soldiers go over the wall as well as entering the front of the house."

The officer looked up twenty feet. The wall was absolutely perpendicular and as smooth as the side of a house.

"I'm afraid none of my men can scale it," he said.

"Can't we throw a grapnel over it, sir?"

"We might; but it would be a very slight hold."

"If you can make it hold at all," laughed Donald, "I'm willing to make the effort. At best I can only fall back into the water."

"True," declared the officer. "We'll try it."

A grapnel was tied to a long line, such as is used in tying the launch to the shore, and after several vain attempts the grapnel caught in the top of the wall.

Donald sprang forward and tested it with his weight and it held. Then, without another word, he braced his feet against the wall and in almost less time than it takes to write it, he was at the top.

"Do you see any one?" asked the officer from below.

"No, sir; but there is the sound of pacing footsteps on the walk that runs along the side of the house."

"Good! Now make fast the grapnel and we will see if there are a dozen men here who can climb to the top."

The dozen were quickly found and they were soon at the top of the wall. The officer finally decided to add to their armament one of the rapid-firers.

"If there is any resistance," he said, "we'll knock the side of the house in."

"What shall I do?" asked Donald.

"You'd better come back into the boat. You can help us to enter the house in front."

Donald slid down the rope and the expedition quickly made a landing. Silently, so as not to alarm those within the house, the men took their way to the front of the mansion, which was at once recognized as one of the finest in Vera Cruz.

"Do you know who lives here?" asked the officer.

"No, sir," replied Donald.

"I was told it was the residence of one of Huerta's generals," said a soldier. "It was pointed out to me the first day we landed."

"Good!" from the officer. "I shall now have no compunction about entering the place."

With Donald and a couple of soldiers, the officer approached the door and gave a vigorous knock.

There was no response and he knocked again.

"Who is there?" finally came a voice, evidently a mozo.

"An American officer. Open the door in the name of the law."

There was a still further delay and then another voice asked: "How do we know it is an officer?"

"Open and find out, before I force the door."

There was a still further delay.

"It's a good thing we guarded the rear," said Donald. "They are evidently trying to gain time to spirit Lieut. Grimes away, thinking it is Gen. Funston."

"True," said the officer. "We'll wait no longer. Corporal, force the door!"

The corporal placed a small stick of dynamite under the door and fixed a fuse.

"Step back a little," he said.

All obeyed, when at the instant the door was thrown open and a hand, in which was an automatic revolver, was thrust out, directly in the face of the officer.

But quick as was the action, Donald was not taken off his guard.

With a single swift blow he struck the weapon into the air.

At the same instant a fusillade from the rear of the house gave evidence that the men stationed upon the wall had done their work.



CHAPTER XXVIII.

BILLIE MAKES A DISCOVERY.

Having released Lieut. Grimes and taken the plotters into custody, the next task was to locate Strong, the mountebank, and to solve the mystery of the box.

Outside the one exclamation which Donald had uttered when he recognized Strong as the third of the plotters, he had not betrayed his secret to any one, and when Lieut. Grimes told his story to Gen. Funston and described the American, Donald vouchsafed no information which might help to apprehend him.

"The plotter told the Mexicans that he could be found at the Hidalgo Hotel whenever he was wanted," explained Lieut. Grimes. "While he may have lied about it, I think we should send a force and try to locate him."

The advice was acted upon and a corporal and four soldiers sent to the hotel, but to no purpose. No such man was known there.

"What was the use of my saying anything about it?" asked Donald of the other two boys when he returned to Santiago's house and narrated to them the story of his evening's adventure. "I was sure he was not there and I have no idea where he is; but we'll find him and the ten thousand dollars given him by the Mexicans for his treachery."

"That's right, Don," was Billie's comment. "If you can get that money and I can get my ten thousand pounds, this trip won't be so bad."

"In the meantime," said Adrian, "I propose that some of us go to bed. It's nearly two o'clock and there is mighty little chance that any one will try to steal the box again."

"I think you are right," said Billie. "We might as well all go. The doctor is still with Santiago and will stay until he is better. It isn't at all likely that any one will try to come into this room while he is here."

Billie voiced the unanimous opinion, and a few minutes later the young people had all sought their beds, leaving instructions with the physician and the servants that they were to be called if any change for the worse occurred in Santiago's condition.

It was probably two hours later, just about daylight, that the entire household was awakened by a terrible shriek and one of the maids rushed out into the patio.

The boys came to their feet with a bound and hurried from their room on the ground floor, while the others appeared at the head of the stairs.

"What is it?" asked Donald as soon as he could quiet the shrieking maid. "What are you yelling about?"

"Oh, senor!" she cried. "I have seen the devil."

"Nonsense," laughed the boy. "You had a nightmare."

"No, senor. It was the devil. He had horns and a tail and he had the little box under his arm. I saw him!"

"The box!" cried Billie. "Quick, Lucia, look and see if the box is gone!"

The girl rushed back into the library and she, too, gave a shriek.

"It's gone!" she cried. "It's gone!"

The boys sprang up the stairs three at a time and into the library. Lucia was right. The box was gone.

"It must be the old boy, sure enough," said Billie, "or at least one of his imps." Then to the maid: "How did he get in?"

"I don't know, senor. I only saw him go out. He went right through the door without opening it."

"Nonsense!" from Donald. "His Satanic majesty might go through a solid door, but the box wouldn't. There is some other explanation."

"But who could it be?" queried Lucia in great fear.

"Some one who knows the house," declared Adrian emphatically. "He may have put on some masquerade costume just to frighten these superstitious servants in case he was discovered."

"I believe Ad is right," agreed Donald. "What do you think, Billie?"

"Maybe, Don; but I have a theory of my own. If I am right, I can work it better if I tell no one."

At this moment the physician entered the room.

"How is Santiago?" asked Donald.

"Better! He has gone to sleep, and if he is not disturbed, I expect him to be greatly improved when he awakens. I should not be surprised if this were the turning point in his illness."

"Then we had all better go down on to the first floor and leave him alone with his nurses."

"I'd give a good deal to know where Strong is," remarked Donald as they were drinking their coffee an hour later.

"So would I," declared Billie. "I believe, if we can find him, we can solve this entire mystery."

"As soon as we finish our coffee," suggested Donald, "let's get busy and find him. He can't be far."

"That's right," said Adrian. "We'll round him up in short order. Hey, Billie?"

"We ought to; but I'll tell you what. You fellows go out and see if you can get a line on him, and I'll hang round the house to see that the devil doesn't come and steal the rest of the house."

"Especially Lucia," laughed Donald.

"That's all right," was the good-natured reply; "but I have an idea that the devil and Strong may have something in common."

"You don't think it was Strong who came and took the box, do you?" queried Adrian.

"I don't know just what I do think, Ad; but I'm going to do a little detective work and I want to give the impression that we are all out. When you fellows go out, don't say anything that would cause any one in hiding to think we are not all going out together. Do you sabe?"

"Sure. I hope you'll get a clue if we do not."

When the others had gone, Billie sat quietly in his room for a long time. He could easily have gone to sleep, as he had had only a couple of hours' rest, but he made up his mind that he would not be caught napping again if anything should happen.

But nothing happened.

The minutes passed into hours and it was rapidly nearing noon when Billie made up his mind that it was a bad job.

"We had our chance at daylight," he muttered, "and now we will not get another. Whoever is after the box, has it and is not going to take any further chance of being caught."

He went out into the patio and looked up at the sun. It was almost in the zenith and the air was stifling.

"Any one would be a fool to go out at this time of day," he mused. "I wonder where the fellows are?"

He stepped back under the shade of the arcade that extended clear around the patio and threw himself onto a stone seat.

"Queer old place," he thought, "and a queer old seat."

He laid his hand on one of the carved arms and mechanically toyed with an eagle's head that formed one of the decorations. To his surprise the head turned in his hand.

"I hope I haven't broken it," he said as he examined it more closely.

It was clearly made to revolve and so he turned it clear around, when of a sudden the arm of the seat fell apart and the bottom collapsed, disclosing to Billie's astonished eyes a pair of stairs.

Almost thrown to the pavement by the giving way of the seat, Billie picked himself up and looked about to see if he were observed.

There was no one in sight and he stooped down and examined the stairs carefully. Then he straightened up and rubbed his chin as a sudden gleam of intelligence passed through his brain.

"So," he muttered, "this is why Santiago dwells in a house that is directly back of the banker's. That was his box and he is the strange man who made the million-dollar deposit in Don Esteban's bank."

Then he stopped and pondered.

"But who stole the box? Not Santiago, for he has not left his room for days. If it was Strong, he must have entered the bank from some direction other than this. I don't understand, but I'm going to make some further investigation."

He reentered his room, buckled on his automatic and took from his suit case—which, by the way, he had located at the railway station along with that of his companions after the occupation of the city by the marines—his electric torch. Then he went out and descended the stairs, which he discovered were twenty-four in number.

Reaching the bottom he found himself upon a landing some six or eight feet square, from the opposite side of which another flight of stairs ascended.

"I reckon I better see where they lead to," was his comment as he slowly began their ascent.

After going up eighteen stairs his head touched the floor above. He counted the remaining steps by the light of his torch and found that there were six more. This would make the floor over his head on an exact level with the floor of Santiago's house.

"It's just as I expected," he muttered. "If I can get through this floor, I shall find myself in Don Esteban's residence—somewhere. But just where? That's the question."

He pushed upon the stone above his head, but it refused to move. Then he held up his torch and examined the ceiling carefully. Whatever the method by which the stones could be moved, it was carefully concealed.

Much chagrined, Billie at length decided to retrace his steps and await the coming of his companions. He reached the landing and crossed over to the steps by which he had descended.

Glancing up, he uttered an exclamation of surprise, for there at the opening and peering down the stairs was Ambrosio, the ape.

With a cry of recognition the simian started to descend the stairs, but at a noise from above he hesitated and then sprang back and out of sight.

An instant later the opening was closed and Billie was left in the darkness, except for the light of his torch.



CHAPTER XXIX.

THE MYSTERY DEEPENS.

While Billie was making his discoveries Donald and Adrian had also been busy.

When they left the house, at Donald's suggestion, they went first to the bank and told Don Esteban about the disappearance of the box and what the maid had seen. He was much disappointed until it was explained to him that they also had another clue.

"We shall spend our time in the slums," said Donald, "while our chum keeps watch at the house. We feel sure that between us we shall solve the mystery."

"I hope so," was Don Esteban's response. "Do you think I might be able to see this man Santiago?"

"I'm afraid not, sir! The doctor wants him to sleep as long as he can. We will let you know later in the day."

Leaving Don Esteban, the boys started for the plaza, intending to play the part of sightseers and visit every place in which a mountebank might reasonably expect to go. They felt certain that Strong would keep away from the more aristocratic places.

Keeping their eyes open and ever on the alert, they wandered about the streets and into many public places, but up to eleven o'clock had made no discovery. Then they entered a cantina for breakfast, purposely choosing one that was little frequented by Americans.

Seating themselves at a table in one corner where they could see without being seen, the boys ordered a hearty breakfast and then turned their attention to the others in the place.

At the table nearest them were three men of ordinary appearance, busy with their meal. Beyond them was an American soldier, who seemed to have dropped in out of curiosity. He was paying very little attention to his meal, but was eyeing a young woman who was seated behind the cash counter.

On the other side of the room, and partially hidden from our boys by the cash counter, was another man, smoking, and evidently waiting for some one. He kept his eye on the door and every once in a while glanced nervously at his watch.

"Not much going on in here," said Donald in English.

"No; but we are a little early. There may be more in before we finish our breakfast."

It was a true prediction, for within the next five minutes as many more persons entered and disposed themselves around the various tables. Then the boys' breakfast was served and for a few minutes they were more absorbed in the food than in the guests.

As Donald raised his eyes for a moment, however, he caught sight of a man talking to the one sitting back of the cash counter. They were evidently arguing about something in an undertone and a minute later the newcomer took a seat with his back to the boys.

"Look!" was Donald's smothered exclamation, "over there by the cashier. Isn't that our man?"

Adrian raised his eyes and gazed hard at the back of the man's head.

"I could tell better if he would remove his hat. It does look like him, but he has disguised himself some way."

"Sure," laughed Donald. "That's part of his trade; but I'm dead sure it is Strong."

"What had we better do?"

"I don't know. He'll recognize us the minute he sees us. If he is keeping away from us, he will leave. If he is not, he may come over and speak to us. There is no reason why he should not, so far as he knows."

"How would it do to make ourselves visible?"

"I hardly know." Then after a pause: "I'll tell you what. As soon as we finish we'll go out, as though we did not see him, but we will be sure to make enough commotion to attract his attention. Then we'll station ourselves where we can see him as he comes out."

"That's all right, Don; but suppose he doesn't come out?"

Donald scratched his head.

"Oh!" he exclaimed, "I knew I had a thought back of that. When he sees us, if he is not trying to avoid us, he will speak to us. If he does not speak to us, we will know there is something wrong and take immediate steps to have him arrested."

"But he may escape."

"How can he?"

"I suppose he could go out through the kitchen if he had to," was the ready reply.

"Yes, I suppose he could. We must do better than that."

"I'll tell you," said Adrian. "I'll go over and speak to that soldier in English. If it is Strong, he will hear me and will involuntarily make some move. If he wants to make himself known, he will. If he does not do so, we will simply sit here till he goes out and then shadow him."

"That sounds good. Go over and say 'Howdy' to the soldier."

Adrian arose from his seat and stepped over to the soldier.

"Hello, partner!" was his somewhat noisy greeting. "Won't you come over to our table?"

"Why, sure, neighbor! I was just thinking that I was getting mighty lonesome."

He arose from his chair and took a seat beside Donald, who had been observing Strong closely. There could be no doubt that he had been attracted by Adrian's voice, but he gave no intimation that he knew the boys.

"Glad to see you," said Donald, without taking his eyes from his man. "Won't you have another cup of coffee?"

"Bet your life, neighbor!" Then as he lighted a fresh cigarette: "Smoke?"

"Never learned!" laughed Donald. "Seems mighty funny down here, doesn't it?"

"Sure does; but you're just as well off without it. Live here?"

"No," replied Adrian; "we were on our way home and got stuck!"

"What's the matter?" asked the soldier, with much concern. "Out of coin?"

"We haven't much; but Gen. Funston has promised to find us passage home in a few days. Our friend saw him early this morning," this latter remark expressly for Strong's ears.

"If he told you he'd do it, he will," said the soldier. "You can bet on him every time."

It was very evident from Strong's actions that he was taking in every word of the conversation, which was in English and in an unusually loud voice. He pretended to eat, then leaned over and said something to his companion, and a minute later arose from the table and hastily quitted the place.

But the boys were not to be fooled. They sprang from the table and hastily followed, Donald throwing a greenback to the cashier which more than doubly paid the bill.

Their sudden action did not escape the soldier, who, attributing it to another cause, also hastily quitted the cantina.

As the boys emerged into the street, they saw Strong hastening away in the direction of the custom house.

"Going to lose himself in the crowd," said Donald. "Don't let him get out of your sight."

"What's the matter?" asked the soldier, running to catch up with the boys. "Ugly greasers?"

"No," replied Donald, "we're shadowing a man who is wanted by Gen. Funston. That's him," pointing; "keep your eye on him."

"I thought you chaps had something on," laughed the soldier. "You can bet on me!"

Now that they approached nearer the center of the business portion of the city, there were more people on the street; but they were so near their quarry that they easily kept him in sight. Only once had he glanced back, but that was enough to convince him that he was followed.

"He's headed for somewhere," said Adrian. "He doesn't expect to get away from us simply by walking."

"Right," agreed Donald. "There he goes into the post office."

"Yes," from Adrian, "and it has two doors. You stop at the first one and I'll run to the other."

He started on a run and the soldier followed suit.

The sight of a man running and a soldier following, quickly attracted attention and pedestrians began to stop and see what the matter might be. In less than a minute a crowd had collected, among them several soldiers, who quickly brought Adrian to a halt.

"What's the matter?" asked one. Then as the soldier came up: "What are you chasing him for?"

"I'm not chasing him," laughed the seeming pursuer. "He and I are after another chap."

The delay occasioned by this interference was not great, but it was sufficient to allow Strong to escape, had it not been for Donald. He had seen the crowd gathering and, realizing what would happen, ran around the other way, just in time to see Strong disappearing around the corner of the street on which the bank was located.

Madly he dashed down the street and turned the corner in time to see Strong enter the big gate leading into the patio of Don Esteban's residence.

Putting on more steam, a couple of minutes later Donald also dashed into the patio; but Strong was nowhere to be seen.

"He must be in the bank," muttered the boy, and he quickly entered the door.

But Strong had disappeared as completely as though the earth had opened and swallowed him up.



CHAPTER XXX.

THE MYSTERY SOLVED.

When the opening at the head of the stairs had closed upon Billie and he realized that he was shut in a subterranean passage, for a minute his heart sank within him.

He had tried to find an opening at the top of the opposite stairs and had failed, and he did not know that he would have any better success in trying to find a way to open the place through which he had descended.

"Nobody on earth knows that I am down here," he thought, "and with Santiago sick and maybe dying, no one on earth probably knows that there is such a passage."

But Billie was not the lad to sit down and cry. He had been in tight places before and he had an abiding faith in his own ability to do things. Therefore, he called up his courage and slowly mounted the stairs leading to Santiago's patio.

At the top of the stairs he found himself confronted by exactly the same condition as he had found on the opposite side.

"But there is this difference," muttered Billie. "I know that there must be some sort of a crack where that slab fell back."

He held the electric bull's-eye close to the stone and scrutinized every spot.

Not a single crack could he spy.

Then he took out his big jack-knife and prodded with it clear across the width of the stairway.

There was nothing but solid stone.

"Looks kind o' desperate," he told himself, "but I have simply got to find an opening."

Again he prodded the place over without result.

"It's no use," he finally said to himself. "If I am to get out of here, help will have to come from somewhere outside. But how can it?"

He sat down on the stairs and thought deeply.

"If it is as I think," he mused, "these stairs have been used recently. The very fact that Ambrosio is prowling around here is proof that Strong must have been here at some time. But where is Strong?"

He slid down several steps and threw the light of his torch across to the opposite stairs.

"Bang!" went something that sounded like a falling stone.

Billie sprang to his feet.

"Click! Bang!" and down the opposite stairway streamed a ray of light.

Billie shut off his electric torch and waited.

Then on the steps there appeared a foot, then another, until a whole human body was in sight. Then "click, snap!" and the light disappeared.

"By George!" exclaimed Billie under his breath, "there's a man on the stairs right opposite to me. Who on earth can it be?"

His first inclination was to turn on the light, but on second thought he decided not to.

"I'll let him set the copy," thought Billie. "It's a mighty good thing to be able to spring the surprise."

He drew his automatic and stood ready for any emergency.

It was still as a tomb.

He could hear his own heart beat and he could also hear the heavy breathing of the other man.

"Sounds like he had been running and was just catching his breath," was Billie's mental comment.

After some minutes the man's breathing became more quiet and Billie heard him slowly descending the stairs.

"This won't do," thought Billie. "He probably has some kind of a light, and if he gets on the landing and I'm up here, I'll be like a man up a tree."

The lad sat down and slowly slid toward the bottom.

Being only a few steps from the landing, Billie was down first. He crowded to the right and listened.

The other was now nearly on the landing. Now he was on the landing, hugging the wall on the side opposite Billie. Now they passed each other, or rather the man passed Billie, for Billie stood perfectly still.

It seemed as though he must hear Billie's breathing, but if he heard anything he must have thought it his own echo, never dreaming that he was not alone in the passage.

Now Billie could hear him ascending the stairs leading to Santiago's house, and his hope rose high.

"He must know how to open the floor," thought Billie. "I'll be right there when he does."

Silently as a cat Billie crept up the stairs behind his unknown companion.

Near the top the man stopped and a minute later he flashed an electric light against the stone overhead. Another minute and he heaved with the top of his head and the slab slid back.

"And now," exclaimed Billie in a deep voice, "put your hands over your head!"

Whether from fear or from the unparalleled surprise caused by hearing a human voice at such a time and in such a place, instead of obeying Billie's command, Strong's hands—for Strong it was—fell limp at his side and his electric torch fell to the stones beneath his feet.

"All right," continued Billy, "if that's the way you feel about it; but just remember that a single false move and I'll cut this automatic loose among your ribs. Now climb out a step at a time."

With face as white as marble at the shock he had just sustained, Strong obeyed implicitly and Billie was soon standing on the stone patio, looking Strong in the face.

"You're a good one, you are," he said sarcastically. "I should think you'd be ashamed to call yourself an American."

"What do you mean?" asked Strong in a trembling voice.

"Why, first of all, stealing from the bank, and then selling your own countrymen to the Mexicans."

"Who have I sold?"

"Do you mean to say that you didn't sell Gen. Funston to the greasers for ten thousand dollars?"

"Of course I do!" in a somewhat stronger voice.

"Perhaps you'll deny that you are Strong, the mountebank. You don't think for one minute that I don't know you in spite of your make-up, do you?"

"No, I'll admit that I'm the mountebank. As for my name that is of small importance in a country like this. But I did not sell Gen. Funston, as you put it. I knew the man I pointed out was not Funston and I knew that as soon as the Mexicans found it out they would let him go. Some one might have told them rightly. As it was I spoiled their game and I got the money. Do you think it any crime to do that?"

"That's a matter I am not in a position to discuss," was Billie's answer. "But how about robbing the bank?"

"I had as much right to the box as any one."

"You'll have to prove that to some one besides me; all I can do is to turn you over to the authorities."

"Never!" cried Strong. "I'll die before I'll rot in a Mexican jail!"

He uttered a peculiar noise and before Billie could imagine what it meant, he felt himself seized from behind by a pair of hairy hands.

He had been in that clutch once before and recognized in an instant that he was in the grip of the ape.

He gave one loud cry for help and then turned loose with his automatic.

The tumult which followed is beyond description. Billie's shout was as nothing compared to the cry of the ape as one of the bullets struck him in the leg and another pierced his foot. Loosing his hold upon the lad, he grabbed for the weapon, but Billie managed to evade him and would undoubtedly have slain the animal had not Strong sprung to his assistance, with the result that in another minute Billie was disarmed.

Ill would the lad have fared then, at the hands of his two assailants, had not the noise attracted to the scene several soldiers, while an instant later came a loud shout as Donald and Adrian dashed into the patio.

On the other side of the square they had heard Billie's shout, followed by the automatic, and had rushed to his aid.

In another minute both Strong and his hairy friend were overcome and securely bound.

"Where did you find him?" asked Donald, pointing to Strong.

"Down there," was Billie's reply, as he pointed toward the still open underground passage way.

"How did he get there?"

"I suppose he entered from a similar entrance in Don Esteban's patio. I have had an idea all the time that there was some reason for the position of these two houses."

"But it doesn't lead into the bank. How could he steal the box out of the vault?"

"There is the real thief!" exclaimed Billie, pointing to the ape. "He sneaked in while Strong kept the bank employes engaged. By some mistake in his understanding he put the envelope back in the bank the next day instead of putting back the box. It was he who crawled through the bars into Santiago's library. He was also the devil who scared the maid almost into fits."

"Well! Well!" exclaimed a voice from the gateway. "I never could have believed it."

The voice was that of Don Esteban, who had entered while Billie was speaking.

"I have come to see this strange man, Santiago Ojeda," he explained. "What says the doctor?"

"Here comes the doctor now," announced Adrian as the physician made his appearance in the gateway. "He can speak for himself."



CHAPTER XXXI.

THE TREASURE OF MONTEZUMA.

The shadows of evening had fallen and a cool breeze was blowing in off the Gulf of Mexico when a group of persons, among whom were the Broncho Rider Boys, gathered around the bedside of the sick man.

It was as the physician had predicted, and when Santiago had awakened after his long sleep, he had regained his senses, although he was very weak. But as the day declined and the heat lessened he had become stronger, and now at his own request, Lucia and her friends drew around to listen to his tale.

At one side of the bed stood Lucia, the three boys and Don Esteban. At the other stood Mr. Black, Josie and the physician, while at the foot of the bed was Strong, with Ambrosio in his arms, and a couple of soldiers who had the mountebank in custody.

"As my daughter knows," began Santiago in a feeble voice, "I am a direct descendant of the great Montezuma. My ancestor was the guardian of the treasure which had been accumulated by the Aztec kings for years. After the overthrow of my race by the Spanish conquerors, there was given to my first great ancestor the keeping of the secret of the source of the gold which had made the city of Anahuac such a rich prize.

"This secret has been handed down through all these generations, the one object being to use this knowledge in freeing Mexico from the Spanish yoke. This secret I, as the last of my race, possess."

The aged man paused, his strength being hardly able to the task he had set himself.

"It is much as I suspected," whispered Don Esteban to Donald, while Lucia bent over and smoothed the brow of the sick man.

"A few years ago," Santiago finally continued, "I began to see an opportunity for the people to assert their rights. In our good Senor Madero I saw the one who should lead the common people out of their bondage. I went to him and offered him all the wealth at my command. He accepted the trust and we began our work. It was at that time that I placed the money with Don Esteban. Also the box, containing the secret of the mine, of which only I and Madero knew.

"You all know what has happened since that time. Madero won, but he was betrayed. His betrayer now seeks to rule the republic, but he can never do it. He must be overthrown."

The aged man became greatly excited and the physician cautioned him to be careful. In a few minutes he became more peaceful and continued:

"I have always been a great friend of the Americans. I admired their integrity and their government. I spent many years of my youth in the United States. I have known many of their great men. I was sure they would be pleased with Madero, and they were. But after he was betrayed, then I began to fear them, as I was told that the usurper, Huerta, had been helped by them."

"Who told you that?" asked Billie, almost without thinking.

"That man there," and Santiago pointed with his long bony finger at the mountebank, Strong. "That man, Francisco Rodriguez, who claims to be an American, but who is a traitor to his country. He fed me with lies, as I now know, and he wormed out of me the secret of Montezuma's Mine."

Again the aged man's excitement nearly overcame him, but again he rallied with an almost superhuman effort.

"It was because of his lies that I made him my trusted agent; but he betrayed me as he has others. It was to him I gave the ten thousand pounds which the young senor took away from my servant, Pablo Ojeda—who is not an Ojeda, but whom I have allowed to use that name. I desire that the money become the property of the young senor," and he feebly extended his hand toward Billie, "who has always been such a good friend to me and mine. The secret of the mine is to be found in the box which I left with Don Esteban. I am getting to be an old man, and if you will now bring in the box, I will turn it over to my daughter Lucia, who is my only descendant."

Don Esteban made no move to comply with the request, but looked at the boys in such a perplexed manner that the sick man was quick to take notice.

"What is it?" he asked, rising on his elbow and looking at Don Esteban with burning gaze. "What is it? Has anything happened to the box?"

"Yes," faltered the banker, "it has been stolen."

"Stolen!" almost shrieked Santiago. "Stolen! Then there stands the thief!" and he pointed to Strong, who stood with blanched face.

"We know that," said Billie, "but the box has been stolen again and no one knows where it has gone."

"You are wrong," muttered Strong. "It has not been stolen. It is in the bank where it always was."

"Impossible!" cried Don Esteban. "How could it be back in the vault?"

"Ask Ambrosio," replied Strong, with a wan smile. "He can tell."

"Of course he cannot tell," almost shouted Don Esteban.

"Then we shall never know; but I am sure the box is there."

"Send for it! Send for it!" cried Santiago. "Send for it at once that I may turn over to my daughter the secret of the mine."

"That you will never be able to do," said Strong. "It has been destroyed."

"Destroyed!" burst from almost every lip. "Destroyed? How?"

Strong shook his head.

"I can't tell. Again you'll have to ask Ambrosio. It is he who destroyed it."

"By George!" exclaimed Billie, "I knew I ought to have killed that monk the first time I had any dealings with him. I'm sorry now that I didn't."

"At any rate," declared Don Esteban, "I shall send for the box."

He turned to Santiago, who had fallen back upon his pillow, and over whom the physician was bending and feeling his pulse.

"I shall send for it at once," he repeated.

Slowly the physician raised his head and loosed his hold upon the sick man's wrist.

"It is too late," he said. "He will not need it. He is dead."

* * * * *

On board a returning army transport bound for New York stood the Broncho Rider Boys casting their last glance shoreward as the sun was setting behind the mountains that form the background of the city of Vera Cruz. Over the city still waved the Stars and Stripes, and as the darkness fell and the tip of Mt. Orizaba gradually faded from sight, Billie turned to the others and in a voice tinged with sadness remarked:

"There's only one thing about the whole country that I admire."

"What's, that?" asked Adrian. "Lucia?"

"No; it's the wholesome respect the Mexicans show for Brigadier-General Funston."

"Yes, and if he is let alone, he'll make them respect the American flag," echoed Donald.

"Long may it wave!" was Adrian's sententious comment.

But it did not wave long over Vera Cruz, for the following November, Huerta having been obliged to leave the country in the meantime and Gen. Carranza having established himself for the time being in the City of Mexico, the American forces were withdrawn and the Carranza forces took possession of Vera Cruz. Some months later Carranza was recognized by the United States, and at this writing is establishing his government, which promises to be a continuation of the one established by Madero.

Thus it will be seen that Santiago's work for his country was productive of good, as are all efforts to bring liberty to the people and to free them from the rule of a few.

Before sailing for home, the boys had the satisfaction of knowing that the man known as Strong had been properly punished, and that, in accordance with Santiago's dying wish, the ten thousand pounds which he had practically given to Billie months before on the Rio Grande, were placed to the lad's credit in the banking house of Don Esteban.

The fate of Ambrosio, the ape which caused so much trouble, was left in the hands of the keeper of the prison to which Strong was sentenced. It is to be hoped that his behavior will improve.

THE END.

———————————————————————————————————-

TRANSCRIBER'S NOTES

Page 48: Removed extra quotation mark.

Page 60: Changed "moso" to "mozo."

Page 62: Changed typo "gaurd" to "guard."

Page 87: Changed typo "variey" to "variety."

Pages 123, 132: Left words "blue-jackets" and "bluejackets" as printed.

Page 140: Added closing quotation mark.

Page 197: Added missing period.

Pages 206, 214, 224: Left words "kipnaped" and "kipnapped" as printed.

THE END