When the housekeeper entered, she appeared even more composed than when Markham had first questioned her. There was something at once sullen and indomitable in her manner, and she looked at me with a slightly challenging expression. Markham merely nodded to her, but Vance stood up and indicated a low tufted Morris chair near the fireplace, facing the front windows. She sat down on the edge of it, resting her elbows on its broad arms.

    "I have some questions to ask you, Mrs. Platz," Vance began, fixing her sharply with his gaze; "and it will be best for everyone if you tell the whole truth. You understand me—eh, what?"

    The easygoing, half-whimsical manner he had taken with Markham had disappeared. He stood before the woman, stern and implacable.

    At his words she lifted her head. Her face was blank, but her mouth was set stubbornly, and a smouldering look in her eyes told of a suppressed anxiety.

    Vance waited a moment and then went on, enunciating each word with distinctness.

    "At what time, on the day Mr. Benson was killed, did the lady call here?"

    The woman's gaze did not falter, but the pupils of her eyes dilated. "There was nobody here."

    "Oh, yes, there was, Mrs. Platz." Vance's tone was assured. "What time did she call?"

    "Nobody was here, I tell you," she persisted.

    Vance lit a cigarette with interminable deliberation, his eyes resting steadily on hers. He smoked placidly until her gaze dropped. Then he stepped nearer to her, and said firmly, "If you tell the truth, no harm will come to you. But if you refuse any information you will find yourself in trouble. The withholding of evidence is a crime, y' know, and the law will show you no mercy."

    He made a sly grimace at Markham, who was watching the proceedings with interest.

    The woman now began to show signs of agitation. She drew in her elbows, and her breathing quickened. "In God's name, I swear it!—there wasn't anybody here." A slight hoarseness gave evidence of her emotion.

    "Let us not invoke the Deity," suggested Vance carelessly. "What time was the lady here?"

    She set her lips stubbornly, and for a whole minute there was silence in the room. Vance smoked quietly, but Markham held his cigar motionless between his thumb and forefinger in an attitude of expectancy.

    Again Vance's impassive voice demanded: "What time was she here?"

    The woman clinched her hands with a spasmodic gesture, and thrust her head forward.

    "I tell you—I swear it—"

    Vance made a peremptory movement of his hand and smiled coldly. "It's no go," he told her. "You're acting stupidly. We're here to get the truth—and you're going to tell us."

    "I've told you the truth."

    "Is it going to be necess'ry for the district attorney here to order you placed in custody?"

    "I've told you the truth," she repeated.

    Vance crushed out his cigarette decisively in an ash receiver on the table.

    "Right-o, Mrs. Platz. Since you refuse to tell me about the young woman who was here that afternoon, I'm going to tell you about her."

    His manner was easy and cynical, and the woman watched him suspiciously.

    "Late in the afternoon of the day your employer was shot the doorbell rang. Perhaps you had been informed by Mr. Benson that he was expecting a caller, what? Anyhow, you answered the door and admitted a charming young lady. You showed her into this room . . . and—what do you think, my dear Madam!—she took that very chair on which you are resting so uncomfortably."

    He paused and smiled tantalizingly.

    "Then," he continued, "you served tea to the young lady and Mr. Benson. After a bit she departed, and Mr. Benson went upstairs to dress for dinner. . . . Y' see, Mrs. Platz, I happen to know."

    He lit another cigarette.

    "Did you notice the young lady particularly? If not, I'll describe her to you. She was rather short—petite is the word. She had dark hair and dark eyes and she was dressed quietly."

    A change had come over the woman. Her eyes stared; her cheeks were now gray; and her breathing had become audible.

    "Now, Mrs. Platz," demanded Vance sharply, "what have you to say?"

    She drew a deep breath. "There wasn't anybody here," she said doggedly. There was something almost admirable in her obstinacy.

    Vance considered a moment. Markham was about to speak but evidently thought better of it and sat watching the woman fixedly.

    "Your attitude is understandable," Vance observed finally. "The young lady, of course, was well known to you, and you had a personal reason for not wanting it known she was here."

    At these words she sat up straight, a look of terror in her face. "I never saw her before!" she cried, then stopped abruptly.

    "Ah!" Vance gave her an amused leer. "You had never seen the young lady before—eh, what? . . . That's quite possible. But it's immaterial. She's a nice girl, though, I'm sure—even if she did have a dish of tea with your employer alone in his home."

    "Did she tell you she was here?" The woman's voice was listless. The reaction to her tense obduracy had left her apathetic.

    "Not exactly," Vance replied. "But it wasn't necess'ry. I knew without her informing me. . . . Just when did she arrive, Mrs. Platz?"

    "About a half hour after Mr. Benson got here from the office." She had at last given over all denials and evasions. "But he didn't expect her—that is, he didn't say anything to me about her coming; and he didn't order tea until after she came."

    Markham thrust himself forward. "Why didn't you tell me she'd been here when I asked you yesterday morning?"

    The woman cast an uneasy glance about the room.

    "I rather fancy," Vance intervened pleasantly, "that Mrs. Platz was afraid you might unjustly suspect the young lady."

    She grasped eagerly at his words. "Yes sir—that was all. I was afraid you might think she—did it. And she was such a quiet, sweet-looking girl. . . . That was the only reason, sir."

    "Quite so," agreed Vance consolingly. "But tell me: did it not shock you to see such a quiet, sweet-looking young lady smoking cigarettes?"

    Her apprehension gave way to astonishment. "Why—yes, sir, it did. . . . But she wasn't a bad girl—I could tell that. And most girls smoke nowadays. They don't think anything of it, like they used to."

    "You're quite right," Vance assured her. "Still young ladies really shouldn't throw their cigarettes in tiled, gas-log fireplaces, should they, now?"

    The woman regarded him uncertainly; she suspected him of jesting. "Did she do that?" She leaned over and looked into the fireplace. "I didn't see any cigarettes there this morning."

    "No, you wouldn't have," Vance informed her. "One of the district attorney's sleuths, d' ye see, cleaned it all up nicely for you yesterday."

    She shot Markham a questioning glance. She was not sure whether Vance's remark was to be taken seriously; but his casualness of manner and pleasantness of voice tended to put her at ease.

    "Now that we understand each other, Mrs. Platz," he was saying, "was there anything else you particularly noticed when the young lady was here? You will be doing her a good service by telling us, because both the district attorney and I happen to know she is innocent."

    She gave Vance a long, shrewd look, as if appraising his sincerity. Evidently the results of her scrutiny were favorable, for her answer left no doubt as to her complete frankness.

    "I don't know if it'll help, but when I came in with the toast, Mr. Benson looked like he was arguing with her. She seemed worried about something that was going to happen and asked him not to hold her to some promise she'd made. I was only in the room a minute and I didn't hear much. But just as I was going out he laughed and said it was only a bluff and that nothing was going to happen."

    She stopped and waited anxiously. She seemed to fear that her revelation might, after all, prove injurious rather than helpful to the girl.

    "Was that all?" Vance's tone indicated that the matter was of no consequence.

    The woman demurred.

    "That was all I heard; but . . . there was a small blue box of jewelry sitting on the table."

    "My word!—a box of jewelry! Do you know whose it was?"

    "No, sir, I don't. The lady hadn't brought it, and I never saw it in the house before."

    "How did you know it was jewelry?"

    "When Mr. Benson went upstairs to dress, I came in to clear the tea things away, and it was still sitting on the table."

    Vance smiled. "And you played Pandora and took a peep—eh, what? Most natural—I'd have done it myself."

    He stepped back and bowed politely.

    "That will be all, Mrs. Platz. . . . And you needn't worry about the young lady. Nothing is going to happen to her."

    When she had left us, Markham leaned forward and shook his cigar at Vance. "Why didn't you tell me you had information about the case unknown to me?"

    "My dear chap!" Vance lifted his eyebrows in protestation. "To what do you refer specifically?"

    "How did you know this St. Clair woman had been here in the afternoon?"

    "I didn't; but I surmised it. There were cigarette butts of hers in the grate; and, as I knew she hadn't been here on the night Benson was shot, I thought it rather likely she had been here earlier in the day. And since Benson didn't arrive from his office until four, I whispered into my ear that she had called sometime between four and the hour of his departure for dinner. . . . An element'ry syllogism, what?"

    "How did you know she wasn't here that night?"

    "The psychological aspects of the crime left me in no doubt. As I told you, no woman committed it—my metaphysical hypotheses again; but never mind. . . . Furthermore, yesterday morning I stood on the spot where the murderer stood and sighted with my eye along the line of fire, using Benson's head and the mark on the wainscot as my points of coinc'dence. It was evident to me then, even without measurements, that the guilty person was rather tall."

    "Very well. . . . But how did you know she left here that afternoon before Benson did?" persisted Markham.

    "How else could she have changed into an evening gown? Really, y' know, ladies don't go about décolletées in the afternoon."

    "You assume, then, that Benson himself brought her gloves and handbag back here that night?"

    "Someone did—and it certainly wasn't Miss St. Clair."

    "All right," conceded Markham. "And what about this Morris chair?—how did you know she sat in it?"

    "What other chair could she have sat in and still thrown her cigarettes into the fireplace? Women are notoriously poor shots, even if they were given to hurling their cigarette stubs across the room."

    "That deduction is simple enough," admitted Markham. "But suppose you tell me how you know she had tea here unless you were privy to some information on the point?"

    "It pos'tively shames me to explain it. But the humiliating truth is that I inferred the fact from the condition of yon samovar. I noted yesterday that it had been used and had not been emptied or wiped off."

    Markham nodded with contemptuous elation.

    "You seem to have sunk to the despised legal level of material clues."

    "That's why I'm blushing so furiously. . . . However, psychological deductions alone do not determine facts in esse, but only in posse. Other conditions must, of course, be considered. In the present instance the indications of the samovar served merely as the basis for an assumption, or guess, with which to draw out the housekeeper."

    "Well, I won't deny that you succeeded," said Markham. "I'd like to know, though, what you had in mind when you accused the woman of a personal interest in the girl. That remark certainly indicated some preknowledge of the situation."

    Vance's face became serious.

    "Markham, I give you my word," he said earnestly, "I had nothing in mind. I made the accusation, thinking it was false, merely to trap her into a denial. And she fell into the trap. But—deuce take it!—I seemed to hit some nail squarely on the head, what? I can't for the life of me imagine why she was frightened. But it really doesn't matter."

    "Perhaps not," agreed Markham, but his tone was dubious. "What do you make of the box of jewelry and the disagreement between Benson and the girl?"

    "Nothing yet. They don't fit in, do they?"

    He was silent a moment. Then he spoke with unusual seriousness. "Markham, take my advice and don't bother with these side issues. I'm telling you the girl had no part in the murder. Let her alone—you'll be happier in your old age if you do."

    Markham sat scowling, his eyes in space. "I'm convinced that you think you know something."

    "Cogito, ergo sum," murmured Vance. "Y' know, the naturalistic philosophy of Descartes has always rather appealed to me. It was a departure from universal doubt and a seeking for positive knowledge in self-consciousness. Spinoza in his pantheism, and Berkeley in his idealism, quite misunderstood the significance of their precursor's favorite enthymeme. Even Descartes' errors were brilliant. His method of reasoning, for all its scientific inaccuracies, gave new signif'cation to the symbols of the analyst. The mind, after all, if it is to function effectively, must combine the mathematical precision of a natural science with such pure speculations as astronomy. For instance, Descartes' doctrine of Vortices—"

    "Oh, be quiet," growled Markham. "I'm not insisting that you reveal your precious information. So why burden me with a dissertation on seventeenth-century philosophy?"

    "Anyhow, you'll admit, won't you," asked Vance lightly, "that, in elim'nating those disturbing cigarette butts, so to speak, I've elim'nated Miss St. Clair as a suspect?"

    Markham did not answer at once. There was no doubt that the developments of the past hour had made a decided impression upon him. He did not underestimate Vance, despite his persistent opposition; and he knew that, for all his flippancy, Vance was fundamentally serious. Furthermore, Markham had a finely developed sense of justice. He was not narrow, even though obstinate at times; and I have never known him to close his mind to the possibilities of truth, however opposed to his own interests. It did not, therefore, surprise me in the least when, at last, he looked up with a gracious smile of surrender.

    "You've made your point," he said; "and I accept it with proper humility. I'm most grateful to you."

    Vance walked indifferently to the window and looked out. "I am happy to learn that you are capable of accepting such evidence as the human mind could not possibly deny."

    I had always noticed, in the relationship of these two men, that whenever either made a remark that bordered on generosity, the other answered in a manner which ended all outward show of sentiment. It was as if they wished to keep this more intimate side of their mutual regard hidden from the world.

    Markham therefore ignored Vance's thrust. "Have you perhaps any enlightening suggestions, other than negative ones, to offer as to Benson's murderer?" he asked.

    "Rather!" said Vance. "No end of suggestions."

    "Could you spare me a good one?" Markham imitated the other's playful tone.

    Vance appeared to reflect. "Well, I should advise that, as a beginning, you look for a rather tall man, cool-headed, familiar with firearms, a good shot, and fairly well known to the deceased—a man who was aware that Benson was going to dinner with Miss St. Clair, or who had reason to suspect the fact."

    Markham looked narrowly at Vance for several moments.

    "I think I understand. . . . Not a bad theory, either. You know, I'm going to suggest immediately to Heath that he investigate more thoroughly Captain Leacock's activities on the night of the murder."

    "Oh, by all means," said Vance carelessly, going to the piano.

    Markham watched him with an expression of puzzled interrogation. He was about to speak when Vance began playing a rollicking French café song which opens, I believe, with     "Ils sont dans les vignes les moineaux."