In less than half an hour Mannix arrived. Heath relinquished his seat to the newcomer and moved to a large chair beneath the windows. Vance had taken a place at the small table on Markham's right where he was able to face Mannix obliquely.

    It was patent that Mannix did not relish the idea of another interview. His little eyes shifted quickly about the office, lingered suspiciously for a moment on Heath, and at last came to rest on the district attorney. He was more vigilant even than during his first visit; and his greeting to Markham, while fulsome, had in it a note of trepidation. Nor was Markham's air calculated to put him at ease. It was an ominous, indomitable Public Prosecutor who motioned him to be seated. Mannix laid his hat and cane on the table and sat down on the edge of his chair, his back as perpendicular as a flagpole.

    "I'm not at all satisfied with what you told me Wednesday, Mr. Mannix," Markham began, "and I trust you won't necessitate me to take drastic steps to find out what you know about Miss Odell's death."

    "What I know!" Mannix forced a smile intended to be disarming. "Mr. Markham—Mr. Markham!" He seemed oilier than usual as he spread his hands in hopeless appeal. "If I knew anything, believe me, I would tell you—positively I would tell you."

    "I'm delighted to hear it. Your willingness makes my task easier. First, then, please tell me where you were at midnight Monday."

    Mannix's eyes slowly contracted until they looked like two tiny shining disks, but otherwise the man did not move. After what seemed an interminable pause, he spoke.

    "I should tell you where I was Monday? Why should I have to do that? . . . Maybe I'm suspected of the murder—yes?"

    "You're not suspected now. But your apparent unwillingness to answer my question is certainly suspicious. Why don't you care to have me know where you were?"

    "I got no reason to keep it from you, y' understand." Mannix shrugged. "I got nothing to be ashamed of—absolutely! . . . I had a lot of accounts to go over at the office—winter-season stocks. I was down at the office until ten o'clock—maybe later. Then at half past ten—"

    "That'll do!" Vance's voice cut in tartly. "No need to drag anyone else into this thing."

    He spoke with a curious significance of emphasis, and Mannix studied him craftily, trying to read what knowledge, if any, lay behind his words. But he received no enlightenment from Vance's features. The warning, however, had been enough to halt him.

    "You don't want to know where I was at half past ten?"

    "Not particularly," said Vance. "We want to know where you were at midnight. And it won't be necess'ry to mention anyone who saw you at that time. When you tell us the truth, we'll know it." He himself had assumed the air of wisdom and mystery that he had deputed to Markham earlier in the afternoon. Without breaking faith with Alys La Fosse, he had sowed the seeds of doubt in Mannix's mind.

    Before the man could frame an answer, Vance stood up and leaned impressively over the district attorney's desk.

    "You know a Miss Frisbee. Lives in 71st Street; accurately speaking—at number 184; to be more exact—in the house where Miss Odell lived; to put it precisely—in Apartment Number 2. Miss Frisbee was a former model of yours. Sociable girl: still charitable to the advances of her erstwhile employer—meanin' yourself. When did you see her last, Mr. Mannix? . . . Take your time about answering. You may want to think it over."

    Mannix took his time. It was a full minute before he spoke, and then it was to put another question.

    "Haven't I got a right to call on a lady—-haven't I?"

    "Certainly. Therefore, why should a question about so obviously correct and irreproachable an episode make you uneasy?"

    "Me uneasy?" Mannix, with considerable effort, produced a grin. "I'm just wondering what you got in your mind, asking me about my private affairs."

    "I'll tell you. Miss Odell was murdered at about midnight Monday. No one came or went through the front door of the house, and the side door was locked. The only way any one could have entered her apartment was by way of Apartment 2; and nobody who knew Miss Odell ever visited Apartment 2 except yourself."

    At these words Mannix leaned over the table, grasping the edge of it with both hands for support. His eyes were wide and his sensual lips hung open. But it was not fear that one read in his attitude; it was sheer amazement. He sat for a moment staring at Vance, stunned and incredulous.

    "That's what you think, is it? No one could've got in or out except by Apartment 2, because the side door was locked?" He gave a short, vicious laugh. "If that side door didn't happen to be locked Monday night, where'd I stand then—huh? Where'd I stand?"

    "I rather think you'd stand with us—with the district attorney." Vance was watching him like a cat.

    "Sure I would!" spat Mannix. "And let me tell you something, my friend: that's just where I stand—absolutely!" He swung heavily about and faced Markham. "I'm a good fellow, y' understand, but I've kept my mouth shut long enough. . . . That side door wasn't locked Monday night. And I know who sneaked out of it at five minutes to twelve!"

    "Ça marche!" murmured Vance, reseating himself and calmly lighting a cigarette.

    Markham was too astonished to speak at once; and Heath sat stock-still, his cigar halfway to his mouth.

    At length Markham leaned back and folded his arms.

    "I think you'd better tell us the whole story, Mr. Mannix." His voice held a quality which made the request an imperative.

    Mannix, too, settled back in his chair.

    "Oh, I'm going to tell it—believe me, I'm going to tell it. You had the right idea. I spent the evening with Miss Frisbee. No harm in that, though."

    "What time did you go there?"

    "After office hours—half past five, quarter to six. Came up in the subway, got off at 72d, and walked over."

    "And you entered the house through the front door?"

    "No. I walked down the alleyway and went in the side door—like I generally do. It's nobody's business who I call on, and what the telephone operator in the front hall don't know don't hurt him."

    "That's all right so far," observed Heath. "The janitor didn't bolt the side door until after six."

    "And did you stay the entire evening, Mr. Mannix?" asked Markham.

    "Sure—till just before midnight. Miss Frisbee cooked the dinner, and I'd brought along a bottle of wine. Social little party—just the two of us. And I didn't go outside the apartment, understand, until five minutes to twelve. You can get the lady down here and ask her. I'll call her up now and tell her to explain the exact situation about Monday night. I'm not asking you to take my word for it—positively not."

    Markham made a gesture dismissing the suggestion.

    "What took place at five minutes to twelve?"

    Mannix hesitated, as if loath to come to the point.

    "I'm a good fellow, y' understand. And a friend's a friend. But—I ask you—is that any reason why I should get in wrong for something I didn't have absolutely nothing to do with?"

    He waited for an answer, but receiving none, continued.

    "Sure, I'm right. Anyway, here's what happened. As I said, I was calling on the lady. But I had another date for later that night; so a few minutes before midnight I said good-bye and started to go. Just as I opened the door I saw someone sneaking away from the Canary's apartment down the little back hall to the side door. There was a light in the hall, and the door of Apartment 2 faces that side door. I saw the fellow as plain as I see you—positively as plain."

    "Who was it?"

    "Well, if you got to know, it was Pop Cleaver."

    Markham's head jerked slightly.

    "What did you do then?"

    "Nothing, Mr. Markham—nothing at all. I didn't think much about it, y' understand. I knew Pop was chasing after the Canary, and I just supposed he'd been calling on her. But I didn't want Pop to see me—none of his business where I spend my time. So I waited quietly till he went out—"

    "By the side door?"

    "Sure. Then I went out the same way. I was going to leave by the front door, because I knew the side door was always locked at night. But when I saw Pop go out that way, I said to myself I'd do the same. No sense giving your business away to a telephone operator if you haven't got to—no sense at all. So I went out the same way I came in. Picked up a taxi on Broadway, and went—"

    "That's enough!" Again Vance's command cut him short.

    "Oh, all right—all right." Mannix seemed content to end his statement at this point. "Only, y' understand, I don't want you to think—"

    "We don't."

    Markham was puzzled at these interruptions, but made no comment.

    "When you read of Miss Odell's death," he said, "why didn't you come to the police with this highly important information?"

    "I should get mixed up in it!" exclaimed Mannix in surprise. "I got enough trouble without looking for it—plenty."

    "An exigent course," commented Markham with open disgust. "But you nevertheless suggested to me, after you knew of the murder, that Cleaver was being blackmailed by Miss Odell."

    "Sure I did. Don't that go to show I wanted to do the right thing by you—giving you a valuable tip?"

    "Did you see anyone else that night in the halls or alleyway?"

    "Nobody—absolutely nobody."

    "Did you hear anyone in the Odell apartment—anyone speaking or moving about, perhaps?"

    "Didn't hear a thing." Mannix shook his head emphatically.

    "And you're certain of the time you saw Cleaver go out—five minutes to twelve?"

    "Positively. I looked at my watch, and I said to the lady: 'I'm leaving the same day I came; it won't be tomorrow for five minutes yet.'"

    Markham went over his story point by point, attempting by various means to make him admit more than he had already told. But Mannix neither added to his statement nor modified it in any detail; and after half an hour's cross-examination he was permitted to go.

    "We've found one missing piece of the puzzle, at any rate," commented Vance. "I don't see now just how it fits into the complete pattern, but it's helpful and suggestive. And, I say, how beautifully my intuition about Mannix was verified, don't y' know!"

    "Yes, of course—your precious intuition." Markham looked at him sceptically. "Why did you shut him up twice when he was trying to tell me something?"

    "O, tu ne sauras jamais," recited Vance. "I simply can't tell you, old dear. Awfully sorry, and all that."

    His manner was whimsical, but Markham knew that at such times Vance was at heart most serious, and he did not press the question. I could not help wondering if Miss La Fosse realized just how secure she had been in putting her faith in Vance's integrity.

    Heath had been considerably shaken by Mannix's story.

    "I don't savvy that side door being unlocked," he complained. "How the hell did it get bolted again on the inside after Mannix went out? And who unbolted it after six o'clock?"

    "In God's good time, my sergeant, all things will be revealed," said Vance.

    "Maybe—and maybe not. But if we do find out, you can take it from me that the answer'll be Skeel. He's the bird we gotta get the goods on. Cleaver is no expert jimmy artist; and neither is Mannix."

    "Just the same, there was a very capable technician on hand that night, and it wasn't your friend the Dude, though he was probably the Donatello who sculptured open the jewel case."

    "A pair of 'em, was there? That's your theory, is it, Mr. Vance? You said that once before; and I'm not saying you're wrong. But if we can hang any part of it on Skeel, we'll make him come across as to who his pal was."

    "It wasn't a pal, Sergeant. It was more likely a stranger."

    Markham sat glowering into space.

    "I don't at all like the Cleaver end of this affair," he said. "There's been something damned wrong about him ever since Monday."

    "And I say," put in Vance, "doesn't the gentleman's false alibi take on a certain shady significance now, what? You apprehend, I trust, why I restrained you from questioning him about it at the club yesterday. I rather fancied that if you could get Mannix to pour out his heart to you, you'd be in a stronger position to draw a few admissions from Cleaver. And behold? Again the triumph of intuition! With what you now know about him, you can chivvy him most unconscionably—eh, what?"

    "And that's precisely what I'm going to do." Markham rang for Swacker. "Get hold of Charles Cleaver," he ordered irritably. "Phone him at the Stuyvesant Club and also his home—he lives round the corner from the club in West 27th Street. And tell him I want him to be here in half an hour, or I'll send a couple of detectives to bring him in handcuffs."

    For five minutes Markham stood before the window, smoking agitatedly, while Vance, with a smile of amusement, busied himself with The Wall Street Journal. Heath got himself a drink of water, and took a turn up and down the room. Presently Swacker reentered.

    "Sorry, Chief, but there's nothing doing. Cleaver's gone into the country somewhere. Won't be back till late tonight."

    "Hell! . . . All right—that'll do." Markham turned to Heath. "You have Cleaver rounded up tonight, Sergeant, and bring him in here tomorrow morning at nine."

    "He'll be here, sir!" Heath paused in his pacing and faced Markham. "I've been thinking, sir; and there's one thing that keeps coming up in my mind, so to speak. You remember that black document box that was setting on the living room table? It was empty; and what a woman generally keeps in that kind of a box is letters and things like that. Well, now, here's what's been bothering me: that box wasn't jimmied open—it was unlocked with a key. And, anyway, a professional crook don't take letters and documents. . . . You see what I mean, sir?"

    "Sergeant of mine!" exclaimed Vance. "I abase myself before you! I sit at your feet! . . . The document box—the tidily opened, empty document box! Of course. Skeel didn't open it—never in this world! That was the other chap's handiwork."

    "What was in your mind about that box, Sergeant?" asked Markham.

    "Just this, sir. As Mr. Vance has insisted right along, there mighta been someone besides Skeel in that apartment during the night. And you told me that Cleaver admitted to you he'd paid Odell a lot of money last June to get back his letters. But suppose he never paid that money; suppose he went there Monday night and took those letters. Wouldn't he have told you just the story he did about buying 'em back? Maybe that's how Mannix happened to see him there."

    "That's not unreasonable," Markham acknowledged. "But where does it lead us?"

    "Well, sir, if Cleaver did take 'em Monday night, he mighta held on to 'em. And if any of those letters were dated later than last June, when he says he bought 'em back, then we'd have the goods on him."

    "Well?"

    "As I say, sir, I've been thinking. . . . Now, Cleaver is outa town today; and if we could get hold of those letters. . . ."

    "It might prove helpful, of course," said Markham coolly, looking the sergeant straight in the eye. "But such a thing is quite out of the question."

    "Still and all," mumbled Heath. "Cleaver's been pulling a lot of raw stuff on you, sir."