Though Vance and I arrived at the district attorney's office the following morning a little after nine, the captain had been waiting twenty minutes; and Markham directed Swacker to send him in at once.

    Captain Philip Leacock was a typical army officer, very tall—fully six feet, two inches—clean-shaven, straight, and slender. His face was grave and immobile; and he stood before the district attorney in the erect, earnest attitude of a soldier awaiting orders from his superior officer.

    "Take a seat, Captain," said Markham, with a formal bow. "I have asked you here, as you probably know, to put a few questions to you concerning Mr. Alvin Benson. There are several points regarding your relationship with him which I want you to explain."

    "Am I suspected of complicity in the crime?" Leacock spoke with a slight southern accent.

    "That remains to be seen," Markham told him coldly. "It is to determine that point that I wish to question you."

    The other sat rigidly in his chair and waited.

    Markham fixed him with a direct gaze.

    "You recently made a threat on Mr. Alvin Benson's life, I believe."

    Leacock started, and his fingers tightened over his knees. But before he could answer, Markham continued: "I can tell you the occasion on which the threat was made—it was at a party given by Mr. Leander Pfyfe."

    Leacock hesitated, then thrust forward his jaw. "Very well, sir; I admit I made the threat. Benson was a cad—he deserved shooting. . . . That night he had become more obnoxious than usual. He'd been drinking too much—and so had I, I reckon."

    He gave a twisted smile and looked nervously past the district attorney out of the window.

    "But I didn't shoot him, sir. I didn't even know he'd been shot until I read the paper next day."

    "He was shot with an army Colt, the kind you fellows carried in the war," said Markham, keeping his eyes on the man.

    "I know," Leacock replied. "The papers said so."

    "You have such a gun, haven't you, Captain?"

    Again the other hesitated. "No, sir." His voice was barely audible.

    "What became of it?"

    The man glanced at Markham and then quickly shifted his eyes. "I—I lost it . . . in France."

    Markham smiled faintly.

    "Then how do you account for the fact that Mr. Pfyfe saw the gun the night you made the threat?"

    "Saw the gun?" He looked blankly at the district attorney.

    "Yes, saw it and recognized it as an army gun," persisted Markham, in a level voice. "Also, Major Benson saw you make a motion as if to draw a gun."

    Leacock drew a deep breath, and set his mouth doggedly.

    "I tell you sir, I haven't a gun. . . . I lost it in France."

    "Perhaps you didn't lose it, Captain. Perhaps you lent it to someone."

    "I didn't sir!" the words burst from his lips.

    "Think a minute, Captain. . . . Didn't you lend it to someone?"

    "No—I did not!"

    "You paid a visit—yesterday—to Riverside Drive. . . . Perhaps you took it there with you."

    Vance had been listening closely. "Oh, deuced clever!" he now murmured in my ear.

    Captain Leacock moved uneasily. His face, even with its deep coat of tan, seemed to pale, and he sought to avoid the implacable gaze of his questioner by concentrating his attention upon some object on the table. When he spoke his voice, heretofore truculent, was colored by anxiety.

    "I didn't have it with me. . . . And I didn't lend it to anyone."

    Markham sat leaning forward over the desk, his chin on his hand, like a minatory graven image. "It may be you lent it to someone prior to that morning."

    "Prior to . . . ?" Leacock looked up quickly and paused, as if analyzing the other's remark.

    Markham took advantage of his perplexity.

    "Have you lent your gun to anyone since you returned from France?"

    "No, I've never lent it—" he began, but suddenly halted and flushed. Then he added hastily, "How could I lend it? I just told you, sir—"

    "Never mind that!" Markham cut in. "So you had a gun, did you, Captain? . . . Have you still got it?"

    Leacock opened his lips to speak but closed them again tightly.

    Markham relaxed and leaned back in his chair.

    "You were aware, of course, that Benson had been annoying Miss St. Clair with his attentions?"

    At the mention of the girl's name the captain's body became rigid; his face turned a dull red, and he glared menacingly at the district attorney. At the end of a slow, deep inhalation he spoke through clenched teeth.

    "Suppose we leave Miss St. Clair out of this." He looked as though he might spring at Markham.

    "Unfortunately, we can't." Markham's words were sympathetic but firm. "Too many facts connect her with the case. Her handbag, for instance, was found in Benson's living room the morning after the murder."

    "That's a lie, sir!"

    Markham ignored the insult.

    "Miss St. Clair herself admits the circumstance." He held up his hand, as the other was about to answer. "Don't misinterpret my mentioning the fact. I am not accusing Miss St. Clair of having anything to do with the affair. I'm merely endeavoring to get some light on your own connection with it."

    The captain studied Markham with an expression that clearly indicated he doubted these assurances. Finally he set his mouth and announced with determination:

    "I haven't anything more to say on the subject, sir."

    "You knew, didn't you," continued Markham, "that Miss St. Clair dined with Benson at the Marseilles on the night he was shot?"

    "What of it?" retorted Leacock sullenly.

    "And you knew, didn't you, that they left the restaurant at midnight, and that Miss St. Clair did not reach home until after one?"

    A strange look came into the man's eyes. The ligaments of his neck tightened, and he took a deep, resolute breath. But he neither glanced at the district attorney nor spoke.

    "You know, of course," pursued Markham's monotonous voice, "that Benson was shot at half past twelve?" He waited, and for a whole minute there was silence in the room.

    "You have nothing more to say, Captain?" he asked at length; "no further explanations to give me?"

    Leacock did not answer. He sat gazing imperturbably ahead of him; and it was evident he had sealed his lips for the time being.

    Markham rose.

    "In that case, let us consider the interview at an end."

    The moment Captain Leacock had gone, Markham rang for one of his clerks.

    "Tell Ben to have that man followed. Find out where he goes and what he does. I want a report at the Stuyvesant Club tonight."

    When we were alone, Vance gave Markham a look of half-bantering admiration.

    "Ingenious, not to say artful. . . . But, y' know, your questions about the lady were shocking bad form."

    "No doubt," Markham agreed. "But it looks now as if we were on the right track. Leacock didn't create an impression of unassailable innocence."

    "Didn't he?" asked Vance. "Just what were the signs of his assailable guilt?"

    "You saw him turn white when I questioned him about the weapon. His nerves were on edge—he was genuinely frightened."

    Vance sighed. "What a perfect ready-made set of notions you have, Markham! Don't you know that an innocent man, when he comes under suspicion, is apt to be more nervous than a guilty one, who, to begin with, had enough nerve to commit the crime and, secondly, realizes that any show of nervousness is regarded as guilt by you lawyer chaps? 'My strength is as the strength of ten because my heart is pure' is a mere Sunday school pleasantry. Touch almost any innocent man on the shoulder and say 'You're arrested,' and his pupils will dilate, he'll break out in a cold sweat, the blood will rush from his face, and he'll have tremors and dyspnea. If he's a hystérique, or a cardiac neurotic, he'll probably collapse completely. It's the guilty person who, when thus accosted, lifts his eyebrows in bored surprise and says, 'You don't mean it, really—here have a cigar.'"

    "The hardened criminal may act as you say," Markham conceded; "but an honest man who's innocent doesn't go to pieces, even when accused."

    Vance shook his head hopelessly. "My dear fellow, Crile and Voronoff might have lived in vain for all of you. Manifestations of fear are the result of glandular secretions—nothing more. All they prove is that the person's thyroid is undeveloped or that his adrenals are subnormal. A man accused of a crime, or shown the bloody weapon with which it was committed, will either smile serenely, or scream, or have hysterics, or faint, or appear disint'rested according to his hormones and irrespective of his guilt. Your theory, d' ye see, would be quite all right if everyone had the same amount of the various internal secretions. But they haven't. . . . Really, y' know, you shouldn't send a man to the electric chair simply because he's deficient in endocrines. It isn't cricket."

    Before Markham could reply, Swacker appeared at the door and said Heath had arrived.

    The sergeant, beaming with satisfaction, fairly burst into the room. For once he forgot to shake hands. "Well, it looks like we've got hold of something workable. I went to this Captain Leacock's apartment house last night, and here's the straight of it:—Leacock was at home the night of the thirteenth all right; but shortly after midnight he went out, headed west—get that!—and he didn't return till about quarter of one!"

    "What about the hallboy's original story?" asked Markham.

    "That's the best part of it. Leacock had the boy fixed. Gave him money to swear he hadn't left the house that night. What do you think of that, Mr. Markham? Pretty crude—huh? . . . The kid loosened up when I told him I was thinking of sending him up the river for doing the job himself." Heath laughed unpleasantly. "And he won't spill anything to Leacock, either."

    Markham nodded his head slowly.

    "What you tell me, Sergeant, bears out certain conclusions I arrived at when I talked to Captain Leacock this morning. Ben put a man on him when he left here, and I'm to get a report tonight. Tomorrow may see this thing through. I'll get in touch with you in the morning, and if anything's to be done, you understand, you'll have the handling of it."

    When Heath had left us, Markham folded his hands behind his head and leaned back contentedly.

    "I think I've got the answer," he said. "The girl dined with Benson and returned to his house afterward. The captain, suspecting the fact, went out, found her there, and shot Benson. That would account not only for her gloves and handbag but for the hour it took her to go from the Marseilles to her home. It would also account for her attitude here Saturday and for the captain's lying about the gun. . . . There. I believe, I have my case. The smashing of the captain's alibi about clinches it."

    "Oh, quite," said Vance airily. "'Hope springs exulting on triumphant wing.'"

    Markham regarded him a moment. "Have you entirely forsworn human reason as a means of reaching a decision? Here we have an admitted threat, a motive, the time, the place, the opportunity, the conduct, and the criminal agent."

    "Those words sound strangely familiar," Vance smiled. "Didn't most of 'em fit the young lady also? . . . And you really haven't got the criminal agent, y' know. But it's no doubt floating about the city somewhere. A mere detail, however."

    "I may not have it in my hand," Markham countered. "But with a good man on watch every minute, Leacock won't find much opportunity of disposing of the weapon."

    Vance shrugged indifferently.

    "In any event, go easy," he admonished. "My humble opinion is that you've merely unearthed a conspiracy."

    "Conspiracy? . . . Good Lord! What kind?"

    "A conspiracy of circumst'nces, don't y' know."

    "I'm glad, at any rate, it hasn't to do with international politics," returned Markham good-naturedly.

    He glanced at the clock. "You won't mind if I get to work? I've a dozen things to attend to and a couple of committees to see. . . . Why don't you go across the hall and have a talk with Ben Hanlon and then come back at twelve thirty? We'll have lunch together at the Bankers' Club. Ben's our greatest expert on foreign extradition and has spent most of his life chasing about the world after fugitives from justice. He'll spin you some good yarns."

    "How perfectly fascinatin'!" exclaimed Vance, with a yawn. But instead of taking the suggestion, he walked to the window and lit a cigarette. He stood for a while puffing at it, rolling it between his fingers, and inspecting it critically.

    "Y'know, Markham," he observed, "everything's going to pot these days. It's this silly democracy. Even the nobility is degen'rating. These Régie cigarettes, now; they've fallen off frightfully. There was a time when no self-respecting potentate would have smoked such inferior tobacco."

    Markham smiled. "What's the favor you want to ask?"

    "Favor? What has that to do with the decay of Europe's aristocracy?"

    "I've noticed that whenever you want to ask a favor which you consider questionable etiquette, you begin with a denunciation of royalty."

    "Observin' fella," commented Vance dryly. Then he, too, smiled. "Do you mind if I invite Colonel Ostrander along to lunch?"

    Markham gave him a sharp look. "Bigsby Ostrander, you mean? . . . Is he the mysterious colonel you've been asking people about for the past two days?"

    "That's the lad. Pompous ass and that sort of thing. Might prove a bit edifyin', though. He's the papa of Benson's crowd, so to speak; knows all parties. Regular old scandalmonger."

    "Have him along, by all means," agreed Markham. Then he picked up the telephone. "Now I'm going to tell Ben you're coming over for an hour or so."