There was nothing much that either of us could say or do, but I thought I observed, on closer acquaintance with Norma, that she had something weighing on her mind. Was it a suspicion of which she had not told us? Evidently she was not prepared to say anything yet, but I determined, rather than try to quiz her, to tell Kennedy, in the hope that she might confide in him what she would not breathe to any one else.

It was perhaps an hour or more later that we returned to Craig. He was still at work, though from his manner it was evident that his investigations had begun to show something, however slight.

"Have you found anything?" asked Everson, eagerly.

"I think I have," returned Craig, measuring his words carefully. "Of course you know the dangers of diving and the view now accepted regarding the rapid effervescence of the gases which are absorbed in the body fluids during exposure to pressure. I think you know that experiment has proved that when the pressure is suddenly relieved the gas is liberated in bubbles within the body. That is what seems to do the harm. His symptoms, as you described them, seemed to indicate that. It is like charged water in a bottle. Take out the cork and the gas inside which has been under pressure bubbles up. In the human body, air and particularly the nitrogen in the air, literally form death bubbles."

Everson said nothing as he regarded Kennedy's face searchingly, and Craig went on: "Set free in the spinal cord, for instance, such bubbles may cause partial paralysis, or in the heart may lead to stoppage of the circulation. In this case I am quite sure that what I have found indicates air in the arteries, the heart, and the blood vessels of the brain. It must have been a case of air embolism, insufflation."

Though Everson seemed all along to have suspected something of the sort, Kennedy's judgment left him quite as much at a loss for an explanation. Kennedy seemed to understand, as he went on:

"I have tried to consider all the ways such a thing could have happened," he considered. "It is possible that air might have been introduced into the veins by a hypodermic needle or other instrument. But I find no puncture of the skin or other evidence that would support that theory. I have looked for a lesion of the lungs, but find none. Then how could it have occurred? Had he done any real deep diving?"

Everson shook his head slowly. "No," he replied. "As I said, it wouldn't have been so incomprehensible if he had. Besides, if we had been diving, we should have been on the lookout. No, Bertram had only tested the apparatus once, after we located the wreck. He didn't much more than go under the surface—nothing like the practice dives we all made up in Long Island Sound before we came down here. He was only testing the pumps and other things to see whether they had stood the voyage. Why, it was nothing at all! I don't see how it could have given any one the 'bends'—much less a fellow like Traynor. Why, I think he could have stood more than Kinsale with a little practice. Kennedy, I can't get it out of my mind that there's something about this that isn't RIGHT."

Craig regarded Everson gravely. "Frankly," he confessed, "I must say that I don't understand it myself—at this distance."

"Would you come out to the Key with me?" hastened Everson, as though grasping at a possible solution.

"I should be delighted to help you in any manner that I can," returned Craig, heartily.

Everson could not find words to express his gratitude as we hurried back to the hotel. In the excitement, I had completely forgotten the despatch from the Star, but now I suddenly realized that here, ready to hand, was the only way of getting out to the Key of Gold and securing the story.

Asta Everson and Norma, especially, were overjoyed at the news that Kennedy had consented to accompany them back to the wreck. Evidently they had great faith in him, from what they had heard at home.

Accordingly, Everson lost no time in preparing to return to the yacht. Nothing more now could be done for poor Traynor, and delay might mean much in clearing up the mystery, if mystery it should prove. We were well on our way toward the landing place before I realized that we were going over much the same route that Kennedy and I had taken the day before to reach the home of Guiteras.

I was just about to say something about it to Kennedy, and of the impression that Norma had made on me, when suddenly a figure darted from around a corner and confronted us. We stopped in surprise. It was no other than Dolores herself—not the quiet, subdued Dolores we had seen the day before, but an almost wild, passionate creature. What it was that had transformed her I could not imagine. It was not ourselves that she seemed to seek, nor yet the Eversons. She did not pause until she had come close to Norma herself.

For a moment the two women, so different in type, faced each other, Dolores fiery with the ardent beauty of her race, Norma pulsating with life and vigor, yet always mistress of herself.

"I warn you!" cried Dolores, unable to restrain herself. "You thought the other was yours—and he was not. Do not seek revenge. He is mine—MINE, I tell you. Win your own back again. I was only making sport of him. But mine—beware!"

For a moment Norma gazed at her, then, without a word, turned aside and walked on. Another instant and Dolores was gone as suddenly as she had appeared. Asta looked inquiringly, but Norma made no attempt at explanation. What did it mean? Had it anything to do with the dispute in the hotel which Kenmore had witnessed?

At the landing we parted for a time with Everson, to return to our hotel and get what little we needed, including Kennedy's traveling laboratory, while Everson prepared quarters for our reception on the yacht.

"What do you make of that Dolores incident?" I hastened to ask the moment we were alone.

"I don't know," he replied, "except that I feel it has an important bearing on the case. There is something that Norma hasn't told us, I fear."

While we waited for a wagon to transfer our goods to the dock, Kennedy took a moment to call up Kenmore on the News. As he turned to me from the telephone, I saw that what he had learned had not helped him much in his idea of the case.

"It was the Interocean Company which had insured the Antilles," was all he said.

Instantly I thought of Kinsale and his former connection. Was he secretly working with them still? Was there a plot to frustrate Everson's plans? At least the best thing to do was to get out to the wreck and answer our many questions at first hand.

The Belle Aventure was a trim yacht of perhaps seventy feet, low, slim, and graceful, driven by a powerful gas-engine and capable of going almost anywhere. An hour later we were aboard and settled in a handsomely appointed room, where Craig lost no time in establishing his temporary traveling crime clinic.

It was quite late before we were able to start, for Everson had a number of commissions to attend to on this his first visit to port since he had set out so blithely. Finally, however, we had taken aboard all that he needed and we slipped out quietly past the castle on the point guarding the entrance to the harbor. All night we plowed ahead over the brilliant, starry, tropical sea, making splendid time, for the yacht was one of the fastest that had ever been turned out by the builders.

Now and then I could see that Kennedy was furtively watching Norma, in the hope that she might betray whatever secret it was she was guarding so jealously. Though she betrayed nothing, I felt sure that it had to do with some member of the expedition and that it was a more than ordinarily complicated affair of the heart. The ladies had retired, leaving us with Everson in the easy wicker chairs on the after-deck.

"I can't seem to get out of my mind, Everson, that meeting with the Spanish girl on the street," suddenly remarked Kennedy, in the hope of getting something by surprise. "You see, I had already heard of a little unpleasantness in a hotel cafe, before the expedition started. Somehow I feel that there must be some connection."

For a moment Everson regarded Kennedy under the soft rays of the electric light under the awning as it swayed in the gentle air, then looked out over the easy swell of the summer sea.

"I don't understand it myself," he remarked, at length, lowering his voice. "When we came down here Dominick knew that girl, Dolores, and of course Kinsale met her right away, too. I thought Gage was head over ears in love with Norma—and I guess he is. Only that night in the cafe I just didn't like the way he proposed a toast to Dolores. He must have met her that day. Maybe he was a bit excited. What she said to-day might mean that it was her fault. I don't know. But since we've been out to the Key I fancy Norma has been pretty interested in Dominick. And Kinsale doesn't hesitate to show that he likes her. It all sets Donald crazy. It's so mixed up. I can't make anything of it. And Norma—well, even Asta can't get anything out of her. I wish to Heaven you could straighten the thing out."

We talked for some time, without getting much more light than Everson had been able at first to shed on the affair, and finally we retired, having concluded that only time and events would enable us to get at the truth.

It was early in the morning that I was wakened by a change in the motion of the boat. There was very little vibration from the engine, but this motion was different. I looked out of the port- hole which had been very cleverly made to resemble a window and found that we had dropped anchor.

The Key of Gold was a beautiful green island, set, like a sparkling gem, in a sea of deepest turquoise. Slender pines with a tuft of green at the top rose gracefully from the wealth of foliage below and contrasted with the immaculate white of the sandy beach that glistened in the morning sun. Romance seemed to breathe from the very atmosphere of the place.

We found that the others on the yacht were astir, too, and, dressing hastily, we went out on deck. Across the dancing waves, which seemed to throw a mocking challenge to the treasure-seekers to find what they covered, we could see the trawler. Already a small power-boat had put out from her and was plowing along toward us.

It was as the boat came alongside us that we met Gage for the first time. He was a tall, clean-cut fellow, but even at a glance I recognized that his was an unusual type. I fancied that both proctors and professors had worried over him when he was in college.

Particularly I tried to discover how he acted when he met Norma. It was easy to see that he was very eager to greet her, but I fancied that there was some restraint on her part. Perhaps she felt that we were watching and was on her guard.

Dominick greeted Everson warmly. He was a man of about thirty-five and impressed one as having seen a great deal of the world. His position as purser had brought him into intimate contact with many people, and he seemed to have absorbed much from them. I could imagine that, like many people who had knocked about a great deal, he might prove a very fascinating person to know.

Kinsale, on the other hand, was a rather silent fellow and therefore baffling. In his own profession of deep-sea diving he was an expert, but beyond that I do not think he had much except an ambition to get ahead, which might be praiseworthy or not, according as he pursued it.

I fancied that next to Everson himself, Norma placed more confidence in Dominick than in any of the others, which seemed to be quite natural, though it noticeably piqued Gage. On the part of all three, Gage, Dominick, and Kinsale, it was apparent that they were overjoyed at the return of Norma, which also was quite natural, for even a treasure-hunt has hours of tedium and there could be nothing tedious when she was about. Asta was undoubtedly the more fascinating, but she was wrapped up in Everson. It was not long before Kennedy and I also fell under the spell of Norma's presence and personality.

We hurried through breakfast and lost no time in accepting Everson's invitation to join him, with the rest, in the little power-boat on a visit to the trawler.

It was Dominick who took upon himself the task of explaining to us the mysteries of treasure-hunting as we saw them. "You see," he remarked, pointing out to us what looked almost like a strangely developed suit of armor, "we have the most recent deep-sea diving- outfit which will enable us to go from two hundred to three hundred feet down—farther, and establish a record if we had to do it. It won't be necessary, though. The Antilles lies in about two hundred and fifty feet of water, we have found. This armor has to be strong, for, with the air pressure inside, it must resist a pressure of nearly half a pound per square inch for each foot we go—to be exact, something like a hundred and five pounds per square inch at the depth of the wreck. Perhaps if Traynor had been diving we might have thought that that was the trouble."

It was the first reference since we arrived to the tragedy. "He had only had the suit on once," went on Dominick, confirming Everson, "and that was merely to test the pumps and valves and joints. Even Kinsale, here, hasn't been down. Still, we haven't been idle. I have something to report. With our instruments we have discovered that the ship has heeled over and that it will be a bit harder job to get into my office and get out the safe than we hoped—but feasible."

Kennedy showed more interest in the diving apparatus than he had shown in anything else so far. The trawler was outfitted most completely as a tender, having been anchored over the exact spot at which the descents were to be made, held by four strong cables, with everything in readiness for action.

I saw him cast a quick glance at the others. For the moment Dominick, Gage, and Kinsale seemed to have forgotten us in their interest explaining to Norma what had been accomplished in her absence. He seized the occasion to make an even closer examination of the complicated apparatus. So carefully had accident been guarded against that even a device for the purification of the air had been installed in the machine which forced the fresh air down to the diver, compressed.

It was this apparatus which I saw Kennedy studying most, especially one part where the air was passed through a small chamber containing a chemical for the removal of carbon dioxide. As he looked up, I saw a peculiar expression on his face. Quickly he removed the chemical, leaving the tube through which the air passed empty.

"I think the air will be pure enough without any such treatment," he remarked, glancing about to be sure no one had observed.

"How is that?" I inquired, eagerly.

"Well, you know air is a mechanical mixture of gases, mainly oxygen and nitrogen. Here's something that gives it an excess of nitrogen and a smaller percentage of oxygen. Nitrogen is the more dangerous gas for one under compressed air. It is the more inert nitrogen that refuses to get out of the blood after one has been under pressure, that forms the bubbles of gas which cause all the trouble, the 'bends,' compressed-air sickness, you know."

"Then that is how Traynor died?" I whispered, coming hastily to the conclusion. "Some one placed the wrong salt in there—took out oxygen, added nitrogen, instead of removing carbon dioxide?"

Norma had turned toward us. It was too early for Kennedy to accuse anybody, whatever might be his suspicions. He could not yet come from under cover. "I think so," was all he replied.

A moment later the group joined us. "No one has been down on the wreck yet?" inquired Craig, at which Everson turned quickly to the three companions he had left in charge, himself anxious to know.

"No," replied Kinsale before any one else could answer. "Mr. Dominick thought we'd better wait until you came back."

"Then I should like to be the first," cut in Craig, to my utter surprise. Remonstrance had no effect with him. Neither Norma nor Asta could dissuade him. As for the rest of us, our objections seemed rather to confirm him in his purpose.

Accordingly, in spite of the danger, which now no one no more than he knew, all the preparations were made for the first dive. With the aid of Kinsale, whom I watched closely, though no more so than Craig, he donned the heavy suit of rubberized reinforced canvas, had the leads placed on his feet and finally was fitted with the metal head and the "bib"—the whole weighing hardly short of three hundred pounds. It was with serious misgiving that I saw him go over the side of the trawler and shoot down into the water with its dark mystery and tragedy.

The moments that he was down seemed interminable. Suspiciously I watched every move that the men made, fearful that they might do something. I longed for the technical knowledge that would have enabled me to handle the apparatus. I tried to quiet my fears by reasoning that Craig must have had perfect confidence in the value of his discovery if he were willing to risk his life on it, yet I felt that at least a show of vigilance on my part might bluff any one off from an attempt to tamper again with the air-supply. I stuck about closely.

Yet, when there came a hasty signal on the indicator from below, although I felt that he had been down for ages, I knew that it had been only a very short time. Could it be a signal of trouble? Had some one again tampered with the apparatus?

Would they never bring him up? It seemed as if they were working fearfully slow. I remembered how quickly he had shot down. What had seemed then only a matter of seconds and minutes now seemed hours. It was only by sheer will power that I restrained myself as I realized that going under the air pressure might be done safely quite fast, that he must come out slowly, by stages, that over the telephone that connected with his helmet he was directing the decompression in accordance with the latest knowledge that medical science had derived of how to avoid the dread caisson disease.

I don't know when I have felt more relief than I did at seeing his weird headgear appear at the surface. The danger from the "bends" might not be entirely over yet, but at least it was Craig himself, safe, at last.

As he came over the side of the trawler I ran to him. It was like trying to greet a giant in that outlandish suit which was so clumsy out of the water. Craig's back was turned to the others, and when I realized the reason I stood aghast. He had brought up a skull and had handed the gruesome thing to me with a motion of secrecy. Meanwhile he hastened to get out of the cumbersome suit, and, to my delight, showed no evidence yet of any bad effects.

That he should have made the descent and returned so successfully I felt must be a surprise to some one. Who was it? I could not help thinking of Kinsale again. Was he working for two masters? Was he still employed by the insurance company? Was this a scheme to capture all the rich salvage of the ship instead of that percentage to which Everson had secured an agreement with the underwriters?

Kennedy lost no time in getting back to the Belle Aventure with the skull which I had concealed for him. It was a strange burden and I was not loath to resign it to him. None of the others, apparently, knew that he had brought up anything with him, and to all questions he replied as though he had merely been testing out the apparatus and, except in a most cursory way, had not made an examination of the ship, although what he had observed confirmed the investigations they had already made from the surface.

In our cabin, Kennedy set to work immediately after opening his traveling laboratory and taking from it a small kit of tools and some materials that looked almost like those for an actor's make- up.

I saw that he wished to be left alone and retired as gracefully as I could, determined to employ the time in watching the others. I found Norma seated in one of the wicker chairs on the after-deck, talking earnestly with Dominick, and, hesitating whether I should interrupt them, I paused between the library and the sumptuously fitted main saloon. I was glad that I did, for just that moment of hesitation was enough for me to surprise a man peering out at them through the curtains of a window, with every evidence of intense dislike of the situation. Looking closer, I saw that it was Gage. Had I expected anything of the sort I should have gone even more cautiously. As it was, though I surprised him, he heard me in time to conceal his real intentions by some trivial action.

It seemed as if our arrival had been succeeded by a growth of suspicion among the members of the little party. Each, as far as I could make out, was now on guard, and, remembering that Kennedy had often said that that was a most fruitful time, since it was just under such circumstances that even the cleverest could not help incriminating himself, I hastened back to let Craig know how matters were. He was at work now on a most grotesque labor, and, as he placed on it the finishing touches, he talked abstractedly.

"What I am using, Walter," he explained, "might be called a new art. Lately science has perfected the difficult process of reconstructing the faces of human beings of whom only the skull or a few bones, perhaps, are obtainable.

"To the unskilled observer a fleshless skull presents little human likeness and certainly conveys no notion of the exact appearance in life of the person to whom it belonged. But by an ingenious system of building up muscles and skin upon the bones of the skull this appearance can be reproduced with scientific accuracy.

"The method, I might say, has been worked out independently by Professor von Froriep, in Germany, and by Dr. Henri Martin, in France. Its essential principle consists in ascertaining from the examination of many corpses the normal thickness of flesh that overlies a certain bone in a certain type of face. From these calculations the scientists by elaborate processes build up a face on the skull."

I watched him, with an uncontrollable fascination. "For instance," he went on, "a certain type of bone always has nearly the same thickness of muscle over it. A very fine needle with graduations of hundredths of an inch is used in these measurements. As I have done here, a great number of tiny plaster pyramids varying in height according to the measurements obtained by these researches are built up over the skull, representing the thickness of the muscles. The next step will be to connect them together by a layer of clay the surface of which is flush with the tips of the pyramids. Then wax and grease paint and a little hair will complete it. You see, it is really scientific restoration of the face. I must finish it. Meanwhile, I wish you would watch Norma. I'll join you in a short time."

Norma was not on deck when I returned, nor did I see any one else for some time. I walked forward, and paused at the door to the little wireless-room on the yacht, intending to ask the operator if he had seen her.

"Where's Mr. Kennedy?" he inquired, before I had a chance to put my own question. "Some one has been in this wireless-room this morning and must have been sending messages. Things aren't as I left them. I think he ought to know."

Just then Everson himself came up from below, his face almost as white as the paint on the sides of his yacht. Without a word, he drew me aside, looking about fearfully as though he were afraid of being overheard. "I've just discovered half a dozen sticks of dynamite in the hold," he whispered, hoarsely, staring wide-eyed at me. "There was a timing device, set for to-night. I've severed it. Where's Kennedy?"

"Your wireless has been tampered with, too," I blurted out, telling what I had just learned.

We looked at each other blankly. Clearly some one had plotted to blow up the yacht and all of us on board. Without another word, I took his arm and we walked toward our state-room, where Kennedy was at work. As we entered the narrow passage to it I heard low voices. Some one was there before us. Kennedy had shut the door and was talking in the hall. As we turned the corner I saw that it was Norma, whom I had forgotten in the surprise of the two discoveries that had been so suddenly made.

As we approached she glanced significantly at Kennedy as if appealing to him to tell something. Before he could speak, Everson himself interrupted, telling of his discovery of the dynamite and of what the wireless operator had found.

There was a low exclamation from Norma. "It's a plot to kidnap me!" she cried, in a smothered voice. "Professor Kennedy—I told you I thought so!"

Everson and I could only look our inquiries at the startling new turn of events.

"Miss Sanford has just been to her state-room," hastily explained Craig. "There she found that some one had carefully packed up a number of her things and hidden them, as if waiting a chance to get them off safely. I think her intuition is correct. There would be no motive for robbery—here."

Vainly I tried to reason it out. As I thought, I recalled that Gage had seemed insanely jealous of both Dominick and Kinsale, whenever he saw either with Norma. Did Gage know more about these mysterious happenings than appeared? Why had he so persistently sought her? Had Norma instinctively fled from his attentions?

"Where are the others?" asked Craig, quickly. I turned to Everson. I had not yet had time to find out.

"Gone back to the trawler," he replied.

"Signal them to come aboard here directly," ordered Craig.

It seemed an interminable time as the message was broken out in flags to the trawler, which was not equipped with the wireless. Even the hasty explanation which Kennedy had to give to Asta Everson, as she came out of her cabin, wondering where Orrin had gone, served only to increase the suspense. It was as though we were living over a powder-magazine that threatened to explode at any moment. What did the treachery of one member of the expedition mean? Above all, who was it?

We had been so intent watching from the deck the all too slow approach of the little power-boat from the trawler that we had paid no attention to what was on our other quarter.

"A tug approaching, sir," reported the man on watch to Everson. "Seems to be heading for us, sir."

We turned to look. Who was she, friend or foe? We knew not what to expect. Everson, pale but with a firm grip on his nerves, did not move from the deck as the power-boat came alongside, and Dominick, Gage, and Kinsale swung themselves up the ladder to us.

"It's the tug of that pilot, Guiteras, sir," interposed the man who had spoken before. Not a word was spoken, though I fancied that a quiet smile flitted over Kennedy's face as we waited.

The tug ranged up alongside us. To my utter astonishment, I saw Dolores, her black eyes eagerly scanning our faces. Was she looking for Gage, I wondered? It was only a moment when the party that had put out from the tug also came tumbling aboard.

"I got your message, Kennedy, and brought Guiteras. He wouldn't join the expedition, but he thought more of his daughter than of anything else."

It was Kenmore, who had at last achieved his wish to get on the treasure-hunt story. Everson looked inquiringly at Craig.

"Message?" repeated Kennedy. "I sent no message."

It was Kenmore's turn to stare. Had some one hoaxed him into a wild-goose chase, after all?

"Nothing? About Dolores being deserted, and—"

"He shall marry my daughter!" boomed a gruff voice as Guiteras shouldered his way through the little group, his hand shooting back to a pocket where bulged a huge Colt.

Like a flash Kennedy, who had been watching, caught his wrist. "Just a second, Captain," he shouted, then turned to us, speaking rapidly and excitedly. "This thing has all been carefully, diabolically laid out. All who stood in the way of the whole of the treasure were to be eliminated. One person has sought to get it all—at any cost."

In Craig's own hand now gleamed a deadly automatic while with the other he held Guiteras's wrist.

"But," he added, tensely, "an insane passion has wrecked the desperate scheme. A woman has been playing a part—leading the man on to his own destruction in order to save the man she really loves."

I looked over at Norma. She was pale and agitated, then burning and nervous by turns. It was only by a most heroic effort that she seemed able to restrain herself, her eyes riveted on Kennedy's face, weighing every word to see whether it balanced with a feeling in her own heart.

"The Antilles," shot out Kennedy, suddenly, "was burned and sunk, not by accident, but with a purpose. That purpose has run through all the events I have seen—the use of Mr. Everson, his yacht, his money, his influence. Come!" He strode down the passage to our state-room, and we followed in awed silence.

"It is a vast, dastardly crime—to get the Mexican millions," he went on, pausing, his hand on the knob of the door while we crowded the narrow passage. "I have brought up from the wreck a skull which I found near a safe, unlocked so that entrance would be easy. The skull shows plainly that the man had been hit on the head by some blunt instrument, crushing him. Had he discovered something that it was inconvenient to know? You have heard the stories of the ill-fated ship—"

Craig flung open the door suddenly. We saw a weird face—the head apparently streaming blood from a ghastly wound. There was a shrill cry beside me.

"It's his ghost—Captain Driggs! God save me—it's his ghost come to haunt me and claim the treasure!"

I turned quickly. Dominick had broken down.

"You were—just leading him on—tell me—Norma." I turned again quickly. It was Gage, who had taken Norma's hand, quivering with excitement.

"You never cared for her?" she asked, with the anxiety that showed how in her heart she loved him.

"Never. It was part of the plot. I sent the message to get her here to show you. I didn't know you were playing a game—"

Suddenly the sharp crack of a pistol almost deafened us in the close passageway. As the smoke cleared, I saw Dolores, her eyes blazing with hatred, jealousy, revenge. In her hand was the pistol she had wrenched from her father.

On the floor across the door-sill sprawled a figure. Dominick had paid the price of his faithlessness to her also.

THE END