So extraordinary and unexpected was the result of the draining of the Dragon Pool, that none of us spoke for several moments.

    I glanced at Markham. He was scowling deeply, and I detected in his expression a look of fear and bafflement, such as one might have in the presence of things unknown. Heath, as was usual whenever he was seriously puzzled, was chewing viciously on his cigar, and staring belligerently. Stamm, whose bulging eyes were focused on the lock in the dam through which the water had disappeared, was leaning rigidly forward, as if transfixed by a startling phenomenon.

    Vance seemed the calmest of us all. His eyebrows were slightly elevated, and there was a mildly cynical expression in his cold gray eyes. Moreover, his lips held the suggestion of a smile of satisfaction, although it was evident from the tensity of his attitude that he had not been entirely prepared for the absence of Montague's body.

    Stamm was the first to speak.

    "I'll be damned!" he muttered. "It's incredible—it's not possible!" He fumbled nervously in the pocket of his sport shirt and drew out a small black South American cigarette which he lit with some difficulty.

    Vance shrugged almost imperceptibly.

    "My word!" he murmured. He, too, reached in his pocket for a cigarette. "Now the search for footprints will be more fascinatin' than ever, Sergeant."

    Heath made a wry face.

    "Maybe yes and maybe no. . . . What about that rock that fell in the pool over there? Maybe our guy's under it."

    Vance shook his head.

    "No, Sergeant. The apex of that piece of rock, as it lies buried in the pool, is, I should say, barely eighteen inches in diameter. It couldn't possibly hide a man's body."

    Stamm took his black cigarette from his mouth and turned in Vance's direction.

    "You're right about that," he commented. "It's not a particularly pleasant subject for conversation, but the fact of the matter is, the bottom of the pool is too hard to have a body driven into it by a rock." He looked back toward the dam. "We'll have to find another explanation for Montague's disappearance."

    Heath was both annoyed and uneasy.

    "All right," he mumbled. Then he turned to Vance. "But there wasn't any footprints here last night—at least Snitkin and I couldn't find 'em."

    "Suppose we take another peep," Vance suggested. "And it might be just as well to hail Snitkin, so that we can go about the task systematically."

    Without a word Heath turned and trotted back down the cement path toward the roadway. We could hear him whistling to Snitkin who was on guard at the gate, a hundred feet or so down the East Road.

    Markham moved nervously a few paces back and forth.

    "Have you any suggestion, Mr. Stamm," he asked, "as to what might have become of Montague?"

    Stamm, with a perplexed frown, again scrutinized the basin of the pool. He shook his head slowly.

    "I can't imagine," he replied, after a moment, "—unless, of course, he deliberately walked out of the pool on this side."

    Vance gave Markham a whimsical smile.

    "There's always the dragon as a possibility," he remarked cheerfully.

    Stamm wheeled about. His face was red with anger, and his lips trembled as he spoke.

    "For the love of Heaven, don't bring that up again!" he pleaded. "Things are bad enough as they are, without dragging in that superstitious hocus-pocus. There simply must be a rational explanation for everything."

    "Yes, yes, to be sure," sighed Vance. "Rationality above all else."

    At this moment I happened to look up at the third-floor balcony of the house, and I saw Mrs. Schwarz and Doctor Holliday step up to Mrs. Stamm and lead her gently back into the house.

    A few seconds later Heath and Snitkin joined us.

    The search for footprints along the level area between us and the high-water mark of the pool took considerable time. Beginning close to the filter on the left, Vance, Snitkin and Heath worked systematically across the level space to the perpendicular edge of the cliff that formed the north wall of the pool, on our right. The area was perhaps fifteen feet square. The section lying nearest to the pool was of encrusted earth, and the strip nearest to where Markham, Stamm and I were standing, at the end of the cement path, was covered with short, irregular lawn.

    When, at length, Vance turned at the edge of the cliff and walked back toward us, there was a puzzled look on his face.

    "There's no sign of a footprint," he remarked. "Montague certainly didn't walk out of the pool at this point."

    Heath came up, solemn and troubled.

    "I didn't think we'd find anything," he grumbled. "Snitkin and I made a pretty thorough search last night, with our flashlights."

    Markham was studying the edge of the cliff.

    "Is there any way Montague might have crawled up on one of those ledges and hopped over to the walk here?" he asked of no one in particular.

    Vance shook his head unhappily.

    "Montague might have been an athlete, but he was no inyala."

    Stamm stood as if in hypnotized reflection.

    "If he didn't get out of the pool at this end," he said, "I don't see how the devil he got out at all."

    "But he did get out, don't y' know," Vance returned. "Suppose we do a bit of pryin' around."

    He led the way toward the filter and mounted its broad coping. We followed him in single file, hardly knowing what to expect. When he was half-way across the filter he paused and looked down at the water-line of the pool. It was fully six feet below the coping of the filter and eight feet below the top of the gates. The filter was of small galvanized wire mesh, backed by a thin coating of perforated porous material which looked like very fine cement. It was obvious that no man could have climbed up the side of the filter to the coping without the aid of an accomplice.

    Vance, satisfied, continued across the filter to the cabañas on the far side of the pool. A cement retaining wall about four feet above the water-level of the pool ran from the end of the filter to the dam.

    "It's a sure thing Montague didn't climb over this wall," Heath observed. "Those flood-lights play all along it, and some one would certainly have seen him."

    "Quite right," agreed Stamm. "He didn't escape from the pool on this side."

    We walked down to the dam, and Vance made a complete inspection of it, testing the strength of the wire mesh over the lock and making sure there was no other opening. Then he went down to the stream bed below the dam, where all the water had now flowed off, and wandered for a while over the jagged, algae-covered rocks.

    "There's no use looking for his body down there," Stamm called to him at length. "There hasn't been enough flow here for the last month to wash as much as a dead cat over the dam."

    "Oh, quite," Vance returned abstractedly, climbing back up the bank to where we stood. "I really wasn't looking for the corpse, d' ye see. Even if there had been a strong flow over the dam, Montague wouldn't have been carried over with it. It would take at least twenty-four hours for his body to come to the surface if he had been drowned."

    "Well, just what were you looking for?" Markham demanded testily.

    "I'm sure I don't know, old dear," Vance replied. "Just sightseein'—and hopin'. . . . Suppose we return to the other side of the pool. That little square of ground over there, without any footprints, is dashed interestin'."

    We retraced our steps, along the retaining wall and over the coping of the filter, to the small tract of low ground beyond.

    "What do you expect to find here, Vance?" Markham asked, with a show of irritation. "This whole section has already been gone over for footprints."

    Vance was serious and reflective.

    "And still, don't y' know, there should be footprints here," he returned with a vague gesture of hopelessness. "The man didn't fly out of the pool. . . ." Suddenly he paused. His eyes were fixed dreamily on the small patch of bare grass at our feet, and a moment later he moved forward several paces and knelt down. After scrutinizing the earth at this point for a few seconds he rose and turned back to us.

    "I thought that slight indentation might bear closer inspection," he explained. "But it's only a right-angle impression which couldn't possibly be a footprint."

    Heath snorted.

    "I saw that last night. But it don't mean anything, Mr. Vance. Looks as if somebody set a box or a heavy suit-case there. But that might have been weeks or months ago. Anyway, it's at least twelve feet from the edge of the pool. So even if it had been a footprint, it wouldn't help us any."

    Stamm threw his cigarette away and thrust his hands deep in his pockets. There was a baffled look on his pale face.

    "This situation has me dumbfounded," he said; "and to tell you the truth, gentlemen, I don't like it. It means more scandal for me, and I've had my share of scandal with this damned swimming pool."

    Vance was looking upward along the cliff before us.

    "I say, Mr. Stamm, would it have been possible, do you think, for Montague to have scaled those rocks? There are several ledges visible even from here."

    Stamm shook his head with finality.

    "No. He couldn't have gone up there on the ledges. They aren't connected and they're too far apart. I got stranded on one of them when I was a kid—couldn't go back and couldn't go on—and it took the pater half a day to get me down."

    "Could Montague have used a rope?"

    "Well . . . yes. It might have been done that way. He was a good athlete, and could have gone up hand over hand. But, damn it, I don't see the point. . . ."

    Markham interrupted him.

    "There may be something in that, Vance. Going up over the cliff is about the only way he could have got out of the pool. And you remember, of course, Leland's telling us how Mrs. McAdam was staring across the pool toward the cliff after Montague had disappeared. And later, when she heard about the splash, she was pretty much upset. Maybe she had some inkling of Montague's scheme—whatever it was."

    Vance pursed his lips.

    "Sounds a bit far-fetched," he observed. "But, after all, the johnny has disappeared, hasn't he? . . . Anyway, we can verify the theory." He turned to Stamm. "How does one get to the top of the cliff from here?"

    "That's easy," Stamm told him. "We can go down to the East Road, and turn up the slope from the Clove. You see, the cliff is highest here, and the plateau slopes quickly away through the Clove and the Indian Life Reservation, till it hits the water-level at Spuyten Duyvil. Ten minutes' walk 'll get us there—if you think it worth while going up."

    "It might be well. We could easily see if there are any footprints along the top of the cliff."

    Stamm led the way back to the East Road, and we walked north toward the gate of the estate. A hundred yards or so beyond the gate we turned off to the west, along a wide footpath which circled northward and swung sharply toward the foot of the Clove. Then the climb up the steep slope to the cliff began. A few minutes later we were standing on the rocks, looking down into the empty basin of the pool, which was about a hundred feet below us. The old Stamm residence, on the hill opposite, was almost level with us.

    One topographical feature of the spot that facilitated matters in looking for footprints was the sheer drop of rocks on either side of a very narrow plateau of earth; and it was only down this plateau—perhaps ten feet across—that any one, even had he scaled the cliff from the pool, could have retreated down the hill to the main road.

    But, although a thorough inspection of the surrounding terrain was made by Vance and Heath and Snitkin, there were no evidences whatever of any footprints, or disturbances, on the surface of the earth that would indicate that anybody had been there since the heavy rains of the night before. Even to my untrained eye this fact was only too plain.

    Markham was disappointed.

    "It's obvious," he admitted hopelessly, "that this method of exit from the pool is eliminated."

    "Yes, I fear so." Vance took out a cigarette and lighted it with studious deliberation. "If Montague left the pool by way of this cliff he must have flown over."

    Stamm swung round, his face pale.

    "What do you mean by that, sir? Are you going back to that silly story of the dragon?"

    Vance raised his eyebrows.

    "Really now, my figure of speech bore no such intimation. But I see what you mean. The Piasa, or Amangemokdom, did have wings, didn't he?"

    Stamm glowered at him, and then gave a grim, mirthless laugh.

    "These dragon stories are getting on my nerves," he apologized. "I'm fidgety today, anyway."

    He fumbled for another cigarette and stepped toward the edge of the cliff.

    "There's that rock I was telling you about." He pointed to a low boulder just at the apex of the cliff. "It was the top of it that fell into the pool last night." He inspected the sides of the boulder for a moment, running his hand under the slight crevasse on a line with the plateau. "I was afraid it would break off at this point, where the strata overlap. This is where Leland and I tried to pry it loose yesterday. We didn't think the top would fall off. But the rest seems pretty solid now, in spite of the rains."

    "Very interestin'." Vance was already making his way down the slope toward the Clove and the East Road.

    When we had reached the narrow cement footpath that led from the road to the pool, Vance, to my surprise, turned into it again. That little section of low ground between the filter and the cliff seemed to fascinate him. He was silent and meditative as he stood at the end of the walk, looking out again over the empty basin of the pool.

    Just behind us, and a little to the right of the walk, I had noticed a small stone structure, perhaps ten feet square and barely five feet high, almost completely covered with English ivy. I had paid scant attention to it and had forgot its existence altogether until Vance suddenly addressed Stamm.

    "What is that low stone structure yonder that looks like a vault?"

    "Just that," Stamm replied. "It's the old family vault. My grandfather had the idea he wanted to be buried here on the estate, so he had it built to house his remains and those of the other members of the family. But my father refused to be buried in it—he preferred cremation and a public mausoleum—and it has not been opened during my lifetime. However, my mother insists that she be placed in it when she dies." Stamm hesitated and looked troubled. "But I don't know what to do about it. All this property will some day be taken over by the city—these old estates can't go on forever, with conditions what they are today. Not like Europe, you know."

    "The curse of our commercial civilization," murmured Vance. "Is there any one besides your grandfather buried in the vault?"

    "Oh, yes." Stamm seemed uninterested. "My grandmother is in one of the crypts. And a couple of aunts are there, I believe, and my grandfather's youngest brother—they died before I was born. It's all duly recorded in the family Bible, though I've never taken the trouble to verify the data. The fact is, I'd probably have to dynamite the iron door if I wanted to get in. I've never known where the key to the vault is."

    "Perhaps your mother knows where the key is," Vance remarked casually.

    Stamm shot him a quick look.

    "Funny you should say that. Mother told me years ago she had hidden the key, so that no one could ever desecrate the vault. She has queer ideas like that at times, all connected with the traditions of the family and the superstitions of the neighborhood."

    "Anything to do with the dragon?"

    "Yes, damn it!" Stamm clicked his teeth. "Some silly idea that the dragon guards the spirits of our dead and that she's assisting him in caring for the dusty remains of the Stamms. You know how such notions possess the minds of the old." (He spoke with irritation, but there was an undercurrent of apology in his voice.) "As for the key, if she ever really did hide it, she's probably forgotten by now where it is."

    Vance nodded sympathetically.

    "It really doesn't matter," he said. "By the by, was the vault ever mentioned, or discussed, before any of your guests?"

    Stamm thought a moment.

    "No," he concluded. "I doubt if any of them even knows it's on the estate. Excepting Leland, of course. You see, the vault's hidden from the house by the trees here, and no one ever comes over to this side of the pool."

    Vance stood looking up contemplatingly at the old Stamm house; and while I was conjecturing as to what was going on in his mind he turned slowly.

    "Really, y' know," he said to Stamm, "I could bear to have a peep at that vault. It sounds rather romantic." He moved off the path through the trees, and Stamm followed him with an air of resigned boredom.

    "Isn't there a path to the vault?" Vance asked.

    "Oh, yes, there's one leading up from the East Road, but it's probably entirely overgrown with weeds."

    Vance crossed the ten or twelve feet between the path and the vault and stood looking at the squat stone structure for several moments. Its tiled roof was slightly peaked, to allow for drainage, but the ivy had long since climbed up to the low cornice. The stone of its walls was the same as that of the Stamm house. On the west elevation was a nail-studded door of hammered iron which, despite its rust and appearance of antiquity, still gave forth an impression of solid impregnability. Leading down to the door were three stone steps, overgrown with moss. As Stamm explained to us, the vault had been built partly underground, so that at its highest point it was only about five feet above the level of the ground.

    Beside the vault, on the side nearest the walk, lay a pile of heavy boards, warped and weather-stained. Vance, after walking round the vault and inspecting it, halted beside the pile of boards.

    "What might the lumber be for?" he asked.

    "Just some timber left over from the water-gates above the filter," Stamm told him.

    Vance had already turned away and started back toward the cement walk.

    "Amazin'," he commented when Stamm had come up to him. "It's difficult to realize that one is actually within the city limits of Manhattan."

    Markham, up to this point, had refrained from any comment, though it was evident to me that he was annoyed at Vance's apparent digressions. Now, however, he spoke with an irritation which reflected his impatience.

    "Obviously there's nothing more we can do here, Vance. Even though there are no footprints, the irresistible inference is that Montague got out of the pool some way—which will probably be explained later, when he's ready to show up. . . . I think we'd better be getting along."

    The very intensity of his tone made me feel that he was arguing against his inner convictions—that, indeed, he was far from satisfied with the turn of events. None the less, there was a leaven of common sense in his attitude, and I myself could see little else to do but to follow his suggestion.

    Vance, however, hesitated.

    "I admit, Markham, that your conclusion is highly rational," he demurred; "but there's something deuced irrational about Montague's disappearance. And, if you don't mind, I think I'll nose about the basin of the pool a bit." Then, turning to Stamm: "How long will the pool remain empty before the stream above the gates overflows?"

    Stamm went to the filter and looked over into the rising water above.

    "I should say another half-hour or so," he reported. "The pool has now been empty for a good hour and a half, and two hours is about the limit. If the gates aren't opened by that time, the stream overflows its banks and runs all over the lower end of the estate and down on the property beyond the East Road."

    "Half an hour will give me ample time," Vance returned. . . . "I say, Sergeant, suppose we fetch those boards from the vault and stretch them out there in the silt. I'd like to snoop at the basin between this point and the place where Montague went in."

    Heath, eager for anything that might lead to some explanation of the incredible situation that confronted us, beckoned Snitkin with a jerk of the head, and the two of them hastened off to the vault. Within ten minutes the boards had been placed end to end, leading from the low land where we stood to the centre of the pool. This had been accomplished by laying one board down first, and then using that as a walk on which to carry the next one which was placed beyond the first board, and so on, until the boards had all been used up. These boards, which were a foot wide and two inches thick, thus formed a dry wooden passage along the floor of the pool, as the muddy silt was not deep enough at any point to overrun the timber.

    During the operation Markham had stood resignedly, his head enveloped in a cloud of cigar smoke.

    "This is just another waste of time," he complained, as Vance turned up the cuffs of his trousers and stepped down the first gently sloping plank. "What, in Heaven's name, do you expect to find out there? You can see the entire bottom of the pool from here."

    Vance gave him a puckish look over the shoulder.

    "To be scrupulously truthful, Markham, I don't expect to find anything. But this pool fascinates me. I really couldn't endure to hobble away without visiting the very seat, so to speak, of the mystery. . . . Come, the Sergeant's bridge is quite dry—or, as you lawyers would say in a legal brief, anhydrous."

    Reluctantly Markham followed him.

    "I'm glad you admit you don't expect to find anything," he mumbled sarcastically. "For a moment I thought you might be looking for the dragon himself."

    "No," smiled Vance. "The Piasa, according to all the traditions, was never able to make himself invisible, although some of the dragons of Oriental mythology were able to change themselves into beautiful women at will."

    Stamm, who was walking just in front of me down the planks, halted and brushed his hand across his forehead.

    "I wish you gentlemen would drop these damnable allusions to a dragon," he objected, in a tone of mingled anger and fear. "My nerves won't stand any more of it this morning."

    "Sorry," murmured Vance. "Really, y' know, we had no intention of upsettin' you."

    He had now come to the end of the last board, a little beyond the centre of the pool, and stood looking about him, shading his eyes with his hand. The rest of us stood in a row beside him. The sun poured down on us unmercifully, and there was not a breath of air to relieve the depressing stagnation of the heat. I was looking past Stamm and Markham at Vance, as his gaze roved over the muddy basin, and I wondered what strange whim had driven him to so seemingly futile an escapade. Despite my respect for Vance's perspicacity and instinctive reasoning, I began to feel very much as I knew Markham felt; and I went so far as to picture a farcical termination to the whole adventure. . . .

    As I speculated I saw Vance suddenly kneel down on the end of the plank and lean forward in the direction of the spring-board.

    "Oh, my aunt!" I heard him exclaim. "My precious doddering aunt!"

    And then he did an astonishing thing. He stepped off the board into the muddy silt and, carefully adjusting his monocle, leaned over to inspect something he had discovered.

    "What have you found, Vance?" called Markham impatiently.

    Vance held up his hand with a peremptory gesture.

    "Just a minute," he returned, with a note of suppressed excitement. "Don't step out here."

    He then walked further away, while we waited in tense silence. After a moment he turned slowly about, toward the cliffs, and came back, following a line roughly parallel with the improvised boardwalk on which we stood. All the time his eyes were fixed on the basin of the pool, and, instinctively, we kept pace with him along the boards as he walked nearer and nearer to the small plot of low ground at the end of the cliff. When he had come within a few feet of the sloping bank he halted.

    "Sergeant," he ordered, "throw the end of that board over here."

    Heath obeyed with alacrity.

    When the board was in place, Vance beckoned to us to step out on it. We filed along the narrow piece of timber in a state of anticipatory excitement; there could be no doubt, from the strained look on Vance's face and the unnatural tone of his voice, that he had made a startling discovery. But none of us could visualize, even at that moment, how grisly and uncanny, how apparently removed from all the sane realities of life, that discovery was to prove.

    Vance leaned over and pointed to a section of the muddy basin of the pool.

    "That's what I've found, Markham! And the tracks lead from beyond the centre of the pool, near the spring-board, all the way back to this low embankment. Moreover, they're confused, and they go in opposite directions. And they circle round in the centre of the pool."

    At first the thing at which Vance pointed was almost indistinguishable, owing to the general roughness of the silt; but as we looked down in the direction of his indicating finger, the horror of it gradually became plain.

    There before us, in the shallow mud, was the unmistakable imprint of what seemed to be a great hoof, fully fourteen inches long, and corrugated as with scales. And there were other imprints like it, to the left and to the right, in an irregular line. But more horrible even that those impressions were numerous demarcations, alongside the hoof-prints, of what appeared to be the three-taloned claw of some fabulous monster.