We arrived at the Stamm estate before ten o'clock. Immediately after calling Vance Markham had left his office and stopped in 38th Street to pick him up. The murder of Montague had taken a powerful hold on Markham's imagination, and the news of Greeff's disappearance had made an irresistible demand on his activities. As he explained to us, driving out in the car, he saw in this new development the first tangible element in the whole affair; and he had now put all his other work aside to take personal charge of the case.

    "I've had my suspicions about Greeff from the first," he said. "There is something sinister in the man; and he has impressed me all along as being involved in Montague's death. Now that he has escaped we can go forward with the investigation with something like a definite aim."

    "I'm not so sure," Vance demurred. He was frowning and smoking thoughtfully. "The case is not going to be so simple even now. Why should Greeff attract suspicion to himself by taking leave of the party? We had no evidence against him; and he must have known that by bolting he would put in operation all the police machinery in the city. Very silly of him, Markham—distressingly silly. And Greeff does not strike me as a silly man."

    "Fear—" Markham began.

    "The man is fearless," Vance interrupted. "It would have been more logical for any other member of the party to have run away. . . . It's most confusin'."

    "The fact remains he's gone," Markham retorted testily. "However, we'll know more when we get there."

    "Oh, quite." And Vance lapsed into silence.

    When we reached the Stamm house Heath greeted us sourly at the entrance.

    "A sweet mess," he complained. "The only guy I had my eye on has made his get-away."

    "Sad . . . sad," sighed Vance. "But console yourself, Sergeant, and unfold your story."

    Heath led the way into the drawing-room and planted himself aggressively before the mantelpiece.

    "First," he said, addressing Markham, "I'd better report on what's been done since yesterday afternoon.—We checked up as best we could on this Bruett woman, but haven't got a trace of her. Furthermore, there hasn't been a boat to South America for four days; so I guess her story to Stamm about sailing was phony. We've checked on all the likely hotels, without any result. And here's a funny one:—she wasn't on the passenger lists of the boats that've arrived from Europe during the past two weeks. Think that over. There's something wrong about that dame, and she'll have a lot of explaining to do when my men locate her."

    Vance smiled tolerantly.

    "I don't wish to dampen your official ardor, Sergeant; but I fear you're not going to find the lady. She's far too sketchy."

    "What do you mean?" snapped Markham. "The automobile on the East Road at the time stated in the note—"

    "It's wholly possible, don't y' know," returned Vance mildly, "that the lady in question wasn't at the wheel. . . . Really, Sergeant, I wouldn't wear my nerves out about her."

    "I'm looking for her, and I'm going to keep on looking for her," Heath asserted with a show of belligerence. Then he turned back to Markham. "We didn't find out anything about Montague except what we already know. Always mixed up with some woman—but what good-looking actor isn't? He always seemed to have money—lived high and spent a lot—but he didn't have many jobs, and no one seems to know where his money came from."

    "Any news about the car on the East Road Saturday night?" asked Markham.

    "Nothing." Heath was disgusted. "We couldn't find any one in Inwood who'd seen it or heard it. And the officer on duty on Payson Avenue says no car came out of Inwood after nine o'clock that night. He was patrolling from eight o'clock on, and could have seen any car that came down the hill. . . . Anyway," Heath added, "it may have coasted down the hill with the lights out."

    "Or," suggested Vance vaguely, "it may never have left Inwood."

    Markham shot him a quick look.

    "What's back of that remark?" he demanded.

    Vance made a slight gesture and shrugged.

    "Oh, I say! Must there be hidden meanings in all my observations? . . . I was merely offering a counter supposition regarding the elusive vehicle."

    Markham grunted.

    "Anything else, Sergeant?"

    "Well, we put the servants here on the carpet—the cook and the maid; and I went over that pasty-faced butler again." Heath made a wry face. "But all I got was the same line of gossip that we've been hearing for a coupla days. They don't know anything, and we can check 'em off the list."

    "The butler," put in Vance, in a quiet tone, "is not without possibilities, Sergeant. He may not know anything, but no one with eyes like his can be devoid of suspicions."

    Heath looked at Vance with a canny squint.

    "You said something, Mr. Vance," he remarked. "But he's too slippery for me. And he's not giving anything away if he can help it."

    "I didn't want to infer, Sergeant," Vance amended, "that you are to pin your faith on him for a solution to the case. I was merely implyin' that the fish-loving Trainor is full of ideas. . . . But, I say, what about the amazin' disappearance of Alex Greeff? His truancy fascinates me."

    Heath drew himself up and took a deep breath.

    "He sneaked away some time during the night. And he was damn slick about it. I stayed here till eleven o'clock, after everybody had gone to their rooms. Then I went home, leaving Snitkin in charge. There was a man at the east gate and one at the front gate all night. Hennessey covered the south border of the estate, and another man from the Bureau was down below the dam watching Bolton Road. I got back here at eight-thirty this morning; and Greeff was gone. I've been in touch with his apartment and his office; but he hasn't showed up at either place. Skipped out clean. . . ."

    "And who," asked Vance, "apprised you of his disappearance?"

    "The butler. He met me at the door—"

    "Ah! The butler—eh, what?" Vance thought a moment. "Suppose we let him chant his own rune."

    "Suits me."

    Heath went from the room, and returned a few minutes later with Trainor. The man's face was ashen. There were deep hollows under his eyes, as if he had not slept for nights; and the flabbiness of his face was like a plastic mask.

    "Was it you, Trainor," asked Vance, "who first discovered Mr. Greeff's absence?"

    "Yes, sir—in a manner of speaking, sir." (He did not meet Vance's direct gaze.) "When Mr. Greeff did not appear for breakfast, Mr. Stamm sent me up-stairs to call him. . . ."

    "What time was that?"

    "About half-past eight, sir."

    "Was every one else down at the time?"

    "Every one, sir. They were all in the dining-room. It was unusually early—if you understand me—but I surmise that no one slept very well last night. Mr. Leland and Miss Stamm were downstairs before seven; and the others followed shortly afterward. Every one but Mr. Greeff, you understand, sir."

    "And they all retired to their rooms early last night?"

    "Yes, sir. Quite early. I put out the down-stairs lights about eleven."

    "Who was the last to retire?"

    "Mr. Stamm, sir. He had been drinking heavily again—if you will forgive me for saying so. But this is no time for reticence—is it, sir?"

    "No, Trainor." Vance was studying the other closely. "Any little detail may be of vital help to us; and I'm sure Mr. Stamm would not construe your information as disloyalty."

    The man seemed relieved.

    "Thank you, sir."

    "And now, Trainor," continued Vance, "tell us about this morning. At half-past eight Mr. Stamm sent you to call Mr. Greeff. And then?"

    "I went to his room, sir—it is just down the hall from Mr. Stamm's—and I knocked. I got no answer, and I knocked again. After I had knocked several times, I got a little worried,—strange things have been happening around here, sir—"

    "Yes, yes. Very strange things, Trainor. But continue. What did you do then?"

    "I—I tried the door, sir." The man's eyes rolled, but he did not look at any one of us. "It was unlocked; and I opened it and looked into the room. . . . I noticed the bed had not been slept in; and I felt a most peculiar sensation—"

    "Spare us your symptoms, Trainor." Vance was becoming impatient. "Tell us what you did."

    "I entered the room, sir, and made sure that Mr. Greeff was not there. Then I returned to the dining-room and indicated to Mr. Stamm that I wished to speak to him alone. He came into the hall, and I informed him of Mr. Greeff's absence."

    "What did Mr. Stamm say?"

    "He didn't say anything, sir. But he had a very queer look on his face. He stood at the foot of the stairs frowning. Then, after a few moments, he pushed me to one side and ran up-stairs. I went back into the dining-room and continued serving the breakfast."

    Heath took up the story at this point.

    "I was in the front hall when Stamm came down," he said. "He was looking queer, all right. But when he saw me he came right up to me and told me about Greeff's being gone. I did a little looking around, and questioned the men on post duty; but they hadn't seen any one leave the estate. Then I phoned to Mr. Markham."

    Vance, for some reason, appeared deeply troubled.

    "Amazin'," he murmured, busying himself with a cigarette. When it was lighted he turned back to the butler. "What time did Mr. Greeff go up-stairs last night?" he asked.

    "I couldn't say exactly, sir." The man was growing noticeably more nervous. "But Mr. Greeff was one of the last to retire."

    "And what time did you yourself go to your quarters?"

    The butler moved forward, thrust out his head, and swallowed with difficulty.

    "Shortly after eleven, sir," he replied in a strained voice. "I closed up the house as soon as this gentleman"—indicating Heath—"had gone. Then I went to my room—"

    "Where is your room?"

    "At the rear of the house, sir, on this floor—next to the kitchen." There was a peculiar intonation in his voice that puzzled me.

    Vance sank deeper into his chair and crossed his knees.

    "I say, Trainor," he drawled, "what did you hear last night, after you had gone to your room?"

    The butler gave a start and sucked in his breath, and his fingers began to twitch. It was several moments before he answered.

    "I heard"—he spoke with a curious mechanical precision—"some one slide the bolt on the side door."

    "The door that leads out to the steps to the pool?"

    "Yes, sir."

    "Did you hear anything else? Any footsteps?"

    Trainor shook his head.

    "No, sir—nothing else." The man's eyes moved vaguely about the room. "Nothing, sir, until an hour or so later—"

    "Ah! And what did you hear then?"

    "I heard the bolt being thrown—"

    "What else?" Vance had risen and was confronting the man sternly.

    Trainor retreated a step or two, and the twitching of his fingers increased.

    "I heard some one go up-stairs—very softly."

    "To which room?"

    "I—I couldn't say, sir."

    Vance gazed at the man indifferently for several seconds; then he turned and walked back to his chair.

    "Who did you think it was?" he asked lazily.

    "It occurred to me that perhaps Mr. Stamm had gone out for a little walk."

    Vance smiled indulgently.

    "Really, y' know, Trainor, if you thought it was Mr. Stamm you wouldn't be so frightfully upset."

    "But who else could it have been, sir?" the man protested weakly.

    Vance was silent for a while.

    "That will be all, Trainor," he said at length. "Tell Mr. Leland we're here and would like to see him."

    "Yes, sir."

    The butler went out, obviously relieved to have the interrogation over; and shortly afterward Leland entered the drawing-room. He was smoking his pipe calmly, and greeted us with more than his usual reserve.

    "You know, of course, Mr. Leland," Vance began, "that Greeff isn't around this morning. Can you suggest any possible explanation for this?"

    Leland appeared worried and sank into a chair by the table.

    "No," he said, "I can see no reason why he should have run off. He is not the kind to run away from anything."

    "Exactly my impression," nodded Vance. "Have you spoken to any of the other persons in the house about it?"

    Leland nodded slowly.

    "Yes, we all discussed it at breakfast and afterwards. Every one seems to be mystified."

    "Did you hear anything during the night that might have indicated when he left the house?"

    Leland hesitated before answering.

    "Yes," he replied finally. "But I also heard something that would indicate that it was not Greeff who went out."

    "You mean the rebolting of the side door an hour or so after it had been unbolted?"

    Leland looked up in mild surprise.

    "Yes," he said. "Just that. Shortly after midnight some one went out the side door, but later some one re-entered the house. I had not been able to go to sleep—and my hearing is particularly keen. . . ."

    "Trainor, too, heard some one go out and come in last night," Vance told him. "But he couldn't tell to what room the midnight prowler returned. Perhaps you are able to enlighten us on that point?"

    Again Leland hesitated, and shook his head slowly.

    "No, I am afraid not," he said. "My room is on the third floor, and several people were moving about below me. I will say this, however: whoever it was that came back to the house was very careful not to make any unnecessary noise."

    Vance had scarcely looked at Leland during the questioning, and he now rose and walked to the front window and back.

    "Is the room you occupy," he asked, "on the side of the house facing the pool?"

    Leland took his pipe leisurely from his mouth and moved uneasily in his chair.

    "Yes, it is just across the side passageway from Mrs. Stamm's quarters."

    "Did you hear any one outside the house after the side door had been opened?"

    "Yes, I did!" Leland sat upright in his chair and carefully repacked his pipe. "I heard voices, as if two people were talking in low tones. But it was only the merest murmur, and I could not distinguish what they were saying or who it was."

    "Could you tell whether it was a man or woman speaking?"

    "No. It seemed to me that they were deliberately pitching their voices to a whisper, to avoid being overheard."

    "How long did this whispered conversation last?"

    "Only a few seconds. Then it faded away."

    "As if the two holding converse were walking away from the house?"

    "Exactly."

    Vance swung about quickly and faced Leland.

    "What else did you happen to hear last night, Mr. Leland?"

    Once again Leland hesitated, and busied himself with relighting his pipe.

    "I am not sure," he answered reluctantly. "But there was a scraping sound at the far side of the pool, toward the East Road."

    "Most interestin'." Vance did not relax his steady gaze. "Will you describe, as nearly as possible, just what you heard."

    Leland looked down at the floor, and smoked intently for a moment.

    "First," he said, "I heard a faint grating noise, as of one piece of metal being rubbed against another—at least, such was my impression. Then all was silence for several minutes. A little later the same sound was repeated and, still later, I could distinguish a low, continuous noise, as of something heavy being dragged over a sandy surface. This noise became fainter and fainter, until finally it died away altogether. . . . I heard nothing more until perhaps half an hour later, when some one re-entered the house through the side door and replaced the bolt."

    "Did these noises strike you as peculiar in any way?"

    "No, I cannot say that they did. We had all been told we had access to the grounds, and I took it for granted, when I heard the side door open, that some one was going out for a walk in the air. The other noises—those on the other side of the pool—were very indistinct and might have been explained in various ways. I knew, of course, that a man had been stationed at the gate on the East Road, and I suppose I assumed—without giving the matter any particular thought—that it was he whom I heard across the pool. It was not until this morning, when I learned of the disappearance of Greeff, that I attached any importance to what I had heard during the night."

    "And now, knowing that Mr. Greeff is gone, can you offer any explanation for the noises you heard?"

    "No, I cannot." Leland thought a moment. "They were not familiar sounds; and while the metallic noise might have been the creaking of the hinges of the gate, there would have been no point in Greeff's opening the gate to make his escape, for he could very easily have climbed over, or walked round it. Moreover, the sound seemed to be much nearer to the house than the gate is. In any event, there was some one guarding the gate, and Greeff would not have chosen that avenue of escape—there are too many other ways of leaving the estate, if he really wished to do so."

    Vance nodded as if satisfied, and again strolled toward the front window.

    "Did you, by any chance," he asked casually, "hear an automobile on the East Road last night?"

    "No." Leland shook his head with emphasis. "I can assure you no car traversed the East Road in either direction up to the time I fell asleep—which, I should say, was about two o'clock in the morning."

    Vance turned leisurely at the window.

    "Did Mr. Greeff," he asked, "by any action or any remark, give you the impression that he contemplated leaving the estate?"

    "Quite the contrary," Leland returned. "He did grouse a bit about being detained here. He said it might mean the loss of some business at his office this morning; but he seemed resigned to seeing the affair through."

    "Did he have any words with any one last night?"

    "No, he was in unusually good humor. He drank a bit more than is his custom, and spent most of the evening, after dinner, discussing financial matters with Stamm."

    "Any evidences of animosity between them?"

    "None whatever. Stamm seemed to have forgotten completely his outburst of the night before."

    Vance walked back and stood before Leland.

    "What of the other members of the party?" he asked. "How did they disport themselves after dinner?"

    "Most of them went out on the terrace. Miss Stamm and I walked down to the pool, but we returned immediately—a pall seemed to hang over it. When we came back to the house, Mrs. McAdam and Miss Steele and young Tatum were sitting on the steps of the terrace, drinking some sort of punch that Trainor had made for them."

    "Where were Greeff and Stamm?"

    "They were still in the library. I doubt if they had gone outdoors at all."

    Vance smoked a moment in thoughtful silence; then he resumed his chair and lay back languidly.

    "Thanks awfully," he said. "That will be all for the present."

    Leland rose.

    "If I can be of any help—" he began, and then contemplated his pipe. Without finishing the sentence he went from the room.

    "What do you make of it, Vance?" Markham asked with a puzzled frown, when we were alone.

    "I don't like it," Vance returned, his eyes on the ceiling. "Too many strange things have been happening in these ancient purlieus. And it's not like Greeff to walk out in the middle of the night. . . ."

    At this moment some one came hurrying down from up-stairs, and a few seconds later we heard Stamm telephoning to Doctor Holliday.

    "You'd better come as soon as you can," he was saying nervously. Then, after a pause, he hung up the receiver.

    Vance had risen and gone to the door.

    "May we see you a moment, Mr. Stamm." His request was practically a command.

    Stamm crossed the hall and entered the drawing-room. It was obvious that he was laboring under some suppressed excitement. The muscles of his face were twitching, and his eyes were staring and restless.

    Before he could speak Vance addressed him.

    "We heard you phoning to the doctor. Is Mrs. Stamm ill again?"

    "The same trouble," Stamm answered. "And it's probably my own fault. I went up to see her a while ago, and I mentioned that Greeff was missing. Then she started in with her pet hallucination. Said he was missing because the dragon had got him. Insisted she saw the dragon rise out of the pool last night and fly down toward Spuyten Duyvil."

    "Most interestin'." Vance leaned against the edge of the table and looked at Stamm through half-closed eyes. "Have you yourself any more rational explanation of Greeff's disappearance?"

    "I can't—understand it." Stamm appeared nonplussed. "From what he said last night he had no intention of leaving the place till you gentlemen gave him permission to go. Seemed quite content to remain here."

    "By the by, did you happen to go outdoors late last night?"

    Stamm looked up with considerable surprise.

    "Didn't leave the house after dinner," he said. "Greeff and I sat in the library chatting till he went up-stairs. I had a nightcap and went to bed very soon after he did."

    "Some one," mused Vance, "let himself out by the side door around midnight."

    "Good God! That must have been when Greeff walked out."

    "But it seems some one came back through the side door an hour or so later."

    Stamm stared with glassy eyes, and his lower lip sagged.

    "You—you're sure?" he stammered.

    "Both Mr. Leland and Trainor heard the bolt being opened and closed," Vance returned.

    "Leland heard it?"

    "So he told us a few minutes ago."

    A change came over Stamm. He drew himself up and made a deprecatory gesture.

    "Probably some one went out for an airing."

    Vance nodded indifferently.

    "That's quite reasonable. . . . Sorry to have bothered you. I presume you want to return to your mother."

    Stamm nodded gratefully.

    "If you don't mind. Doctor Holliday is coming right over. If you want me I'll be up-stairs." And he hurried from the room.

    When the sound of his footsteps had died out up the stairs, Vance suddenly rose and threw his cigarette into the grate.

    "Come, Markham," he said with animation, moving toward the door.

    "Where are you going now?" Markham demanded.

    Vance turned at the portières. His eyes were cold and hard.

    "To the pot-holes," he said quietly.