It was in the cold bleak autumn following the spectacular Dragon murder case that Philo Vance was confronted with what was probably the subtlest and most diabolical criminal problem of his career. Unlike his other cases, this mystery was one of poisoning. But it was not an ordinary poisoning case: it involved far too clever a technique, and was thought out to far too many decimal points, to be ranked with even such famous crimes as the Cordelia Botkin, Molineux, Maybrick, Buchanan, Bowers and Carlyle Harris cases.

    The designation given to it by the newspapers—namely, the Casino murder case—was technically a misnomer, although Kinkaid's famous gambling Casino in West 73rd Street played a large part in it. In fact, the first sinister episode in this notorious crime actually occurred beside the high-stake roulette table in the "Gold Room" of the Casino; and the final episode of the tragedy was enacted in Kinkaid's walnut-paneled Jacobean office, just off the main gambling salon.

    Incidentally, I may say that that last terrible scene will haunt me to my dying day and send cold shivers racing up and down my spine whenever I let my mind dwell on its terrifying details. I have been through many shocking and unnerving situations with Vance during the course of his criminal investigations, but never have I experienced one that affected me as did that terrific and fatal dénouement that came so suddenly, so unexpectedly, in the gaudy environment of that famous gambling rendezvous.

    And Markham, too, I know, underwent some chilling metamorphosis in those few agonizing moments when the murderer stood before us and cackled in triumph. To this day, the mere mention of the incident makes Markham irritable and nervous—a fact which, considering his usual calm, indicates clearly how deep and lasting an impression the tragic affair made upon him.

    The Casino murder case, barring that one fatal terminating event, was not so spectacular in its details as many other criminal cases which Vance had probed and solved. From a purely objective point of view it might even have been considered commonplace; for in its superficial mechanism it had many parallels in well-known cases of criminological history. But what distinguished this case from its many antetypes was the subtle inner processes by which the murderer sought to divert suspicion and to create new and more devilish situations wherein the real motive of the crime was to be found. It was not merely one wheel within another wheel: it was an elaborate and complicated piece of psychological machinery, the mechanism of which led on and on, almost indefinitely, to the most amazing—and erroneous—conclusions.

    Indeed, the first move of the murderer was perhaps the most artful act of the entire profound scheme. It was a letter addressed to Vance thirty-six hours before the mechanism of the plot was put in direct operation. But, curiously enough, it was this supreme subtlety that, in the end, led to the recognition of the culprit. Perhaps this act of letter-writing was too subtle: perhaps it defeated its own purpose by calling mute attention to the mental processes of the murderer, and thereby gave Vance an intellectual clue which fortunately diverted his efforts from the more insistent and more obvious lines of ratiocination. In any event, it achieved its superficial object; for Vance was actually a spectator of the first thrust, so to speak, of the villain's rapier.

    And, as an eye witness to the first episode of this famous poison murder mystery, Vance became directly involved in the case; so that, in this instance, he carried the problem to John F.-X. Markham, who was then the District Attorney of New York County and Vance's closest friend; whereas, in all his other criminal investigations, it was Markham who had been primarily responsible for Vance's participation.

    The letter of which I speak arrived in the morning mail on Saturday, October 15. It consisted of two typewritten pages, and the envelop was postmarked Closter, New Jersey. The official post-office stamp showed the mailing time as noon of the preceding day. Vance had worked late Friday night, tabulating and comparing the æsthetic designs on Sumerian pottery in an attempt to establish the cultural influences of this ancient civilization,[1] and did not arise till ten o'clock on Saturday. I was living in Vance's apartment in East 38th Street at the time; and though my position was that of legal adviser and monetary steward I had, during the past three years, gradually taken over a kind of general secretaryship in his employ. "Employ" is perhaps not the correct word, for Vance and I had been close friends since our Harvard days; and it was this relationship that had induced me to sever my connection with my father's law firm of Van Dine, Davis and Van Dine and to devote myself to the more congenial task of looking after Vance's affairs.

    On that raw, almost wintry, morning in October I had, as usual, opened and segregated his mail, taking care of such items as came under my own jurisdiction, and was engaged in making out his entry blanks for the autumn field trials,[2] when Vance entered the library and, with a nod of greeting, sat down in his favorite Queen-Anne chair before the open fire.

    That morning he was wearing a rare old mandarin robe and Chinese sandals, and I was somewhat astonished at his costume, for he rarely came to breakfast (which invariably consisted of a cup of Turkish coffee and one of his beloved Régie cigarettes) in such elaborate dress.

    "I say, Van," he remarked, when he had pushed the table-button for Currie, his aged English butler and majordomo; "don't look so naïvely amazed. I felt depressed when I awoke. I couldn't trace the designs on some of the jolly old stelæ and cylinder seals they've dug up at Ur, and in consequence had a restless night. Therefore, I bedecked myself in this Chinese attire in an effort to counteract my feelin's, and in the hope, I may add, that I would, through a process of psychic osmosis, acquire a bit of that Oriental calm that is so highly spoken of by the Sinologists."

    At this moment Currie brought in the coffee. Vance, after lighting a Régie and taking a few sips of the thick black liquid, looked toward me lazily and drawled: "Any cheerin' mail?"

    So interested had I been in the strange anonymous letter which had just arrived—although I had as yet no idea of its tragic significance—that I handed it to him without a word. He glanced at it with slightly raised eyebrows, let his gaze rest for a moment on the enigmatic signature, and then, placing his coffee cup on the table, read it through slowly. I watched him closely during the process, and noted a curiously veiled expression in his eyes, which deepened and became unusually serious as he came to the end.

    The letter is still in Vance's files, and I am quoting it here verbatim, for in it Vance found one of his most valuable clues—a clue which, though it did not actually lead to the murderer at the beginning, at least shunted Vance from the obvious line of research intended by the plotter. As I have just said, the letter was typewritten; but the work was inexpertly done—that is, there was evidence of the writer's unfamiliarity with the mechanism of a typewriter. The letter read:

    DEAR MR. VANCE: I am appealing to you for help in my distress. And I am also appealing to you in the name of humanity and justice. I know you by reputation—and you are the one man in New York who may be able to prevent a terrible catastrophe—or at least to see that punishment is meted out to the perpetrator of an impending crime. Horrible black clouds are hovering over a certain household in New York—they have been gathering for years—and I know that the storm is about to break. There is danger and tragedy in the air. Please do not fail me at this time, although I admit I am a stranger to you.

    I do not know exactly what is going to happen. If I did I could go to the police. But any official interference now would put the plotter on guard and merely postpone the tragedy. I wish I could tell you more—but I do not know any more. The thing is all frightfully vague—it is like an atmosphere rather than a specific situation. But it is going to happen—something is going to happen—and whatever does happen will be deceptive and untrue. So please don't let appearances deceive you. Look—look—beneath the thing for the truth. All those involved are abnormal and tricky. Don't underestimate them.

    Here is all I can tell you—

    You have met young Lynn Llewellyn—that much I know—and you probably know of his marriage three years ago to the beautiful musical-comedy star, Virginia Vale. She gave up her career and she and Lynn have been living with his family. But the marriage was a terrible mistake, and for three years a tragedy has been brewing. And now things have come to a climax. I have seen the terrible forms taking shape. And there are others besides the Llewellyns in the picture.

    There is danger—awful danger—for some one—I don't know just who. And the time is tomorrow night, Saturday.

    Lynn Llewellyn must be watched. And watched carefully.

    There is to be a dinner at the Llewellyn home tomorrow night—and every principal in this impending tragedy will be present—Richard Kinkaid, Morgan Bloodgood, young Lynn and his unhappy wife, and Lynn's sister Amelia, and his mother. The occasion is the mother's birthday.

    Although I know that there will be a rumpus of some kind at that dinner, I realize that you can do nothing about it. It will not matter anyway. The dinner will be only the beginning of things. But something momentous will happen later. I know it will happen. The time has now come.

    After dinner Lynn Llewellyn will go to Kinkaid's Casino to play. He goes every Saturday night. I know that you yourself often visit the Casino. And what I beg of you to do is to go there tomorrow night. You must go. And you must watch Lynn Llewellyn—every minute of the time. Also watch Kinkaid and Bloodgood.

    You may wonder why I do not take some action in the matter myself; but I assure you my position and the circumstances make it utterly impossible.

    I wish I could be more definite. But I do not know any more to tell you. You must find out.

    The signature, also typewritten, was "One Deeply Concerned."

    When Vance had perused the letter a second time he settled deep in his chair and stretched his legs out lazily.

    "An amazin' document, Van," he drawled, after several meditative puffs on his cigarette. "And quite insincere, don't y' know. A literary touch here and there—a bit of melodrama—a few samples of gaudy rhetoric—and, occasionally, a deep concern. . . . Quite, oh, quite: the signature, though vague, is genuine. Yes . . . yes—that's quite obvious. It's more heavily typed than the rest of the letter—more pressure on the keys. . . . Passion at work. And not a pleasant passion: a bit of vindictiveness, as it were, coupled with anxiety. . . ." His voice trailed off. "Anxiety!" he continued, as if to himself. "That's exactly what exudes from between the lines. But anxiety about what? about whom? . . . The gambling Lynn? It might be, of course. And yet . . ." Again his voice trailed off, and once more he inspected the letter, adjusting his monocle carefully and scrutinizing both sides of the paper. "The ordin'ry commercial bond," he observed. "Available at any stationer's. . . . And a plain envelop with a pointed flap. My anxious and garrulous correspondent was most careful to avoid the possibility of being traced through his stationer. . . . Very sad. . . . But I do wish the epistler had gone to business school at some time. The typing is atrocious: bad spacings, wrong keys struck, no sense of margin or indentation—all indicative of too little familiarity with the endless silly gadgets of the typewriter."

    He lighted another cigarette and finished his coffee. Then he settled back in his chair and read the letter for the third time. I had seldom seen him so interested. At length he said:

    "Why all the domestic details of the Llewellyns, Van? Any one who reads the newspapers knows of the situation in the Llewellyn home. The pretty blond actress marrying into the Social Register over the protests of mama and then ending up under mama's roof: Lynn Llewellyn a young gadabout and the darling of the night-clubs: serious little sister turning from the frivolities of the social whirl to study art:—who in this fair bailiwick could have failed to hear of these things? And mama herself is a noisy philanthropist and a committee member of every social and economic organization she can find. And certainly Kinkaid, the old lady's brother, is not an inconnu. There are few characters in the city more notorious than he—much to old Mrs. Llewellyn's chagrin and humiliation. The wealth of the family alone would make its doings common gossip." Vance made a wry face. "And yet my correspondent reminds me of these various matters. Why? Why the letter at all? Why am I chosen as the recipient? Why the flowery language? Why the abominable typing? Why this paper and the secrecy? Why everything? . . . I wonder . . . I wonder. . . ."

    He rose and paced up and down. I was surprised at his perturbation: it was altogether unlike him. The letter had not impressed me very much, aside from its unusualness; and my first inclination was to regard it as the act of a crank or of some one who had a grudge against the Llewellyns and was taking this circuitous means of causing them annoyance. But Vance evidently had sensed something in the letter that had completely escaped me.

    Suddenly he ceased his contemplative to-and-fro, and walked to the telephone. A few moments later he was speaking with District Attorney Markham, urging him to stop in at the apartment that afternoon.

    "It's really quite important," he said, with but a trace of the usual jocular manner he assumed when speaking to Markham. "I have a fascinatin' document to show you. . . . Toddle up—there's a good fellow."

    For some time after he had replaced the receiver Vance sat in silence. Finally he rose and turned to the section of his library devoted to psychoanalysis and abnormal psychology. He ran through the indices of several books by Freud, Jung, Stekel and Ferenczi; and, marking several pages, he sat down again to peruse the volumes. After an hour or so he replaced the books on the shelves, and spent another thirty minutes consulting various reference books, such as "Who's Who," the New York "Social Register" and "The American Biographical Dictionary." Finally he shrugged his shoulders slightly, yawned mildly and settled himself at his desk, on which were spread numerous reproductions of the art works unearthed in Doctor Woolley's seven years' excavations at Ur.

    Saturday being a half-day at the District Attorney's office, Markham arrived shortly after two o'clock. Vance meanwhile had dressed and had his luncheon, and he received Markham in the library.

    "A sear and yellow day," he complained, leading Markham to a chair before the fireplace. "Not good for man to be alone. Depression rides me like a hag. I missed the field trial on Long Island today. Preferred to stay in and hover over the glowin' embers. Maybe I'm getting old and full of dreams. . . . Distressin'. . . . But I'm awfully grateful and all that for your comin'. How about a pony of 1811 Napoléon to counteract your autumnal sorrows?"

    "I've no sorrows today, autumnal or otherwise," Markham returned, studying Vance closely. "And when you babble most you're thinking hardest—the unmistakable symptom." (He still scrutinized Vance.) "I'll take the cognac, however. But why the air of mystery over the phone?"

    "My dear Markham—oh, my dear Markham! Really, now, was it an air of mystery? The melancholy days—"

    "Come, come, Vance." Markham was beginning to grow restless. "Where's that interesting paper you wished me to see?"

    "Ah, yes—quite." Vance reached into his pocket, and, taking out the anonymous letter he had received that morning, handed it to Markham. "It really should not have come on a depressin' day like this."

    Markham read the letter through casually and then tossed it on the table with a slight gesture of irritation.

    "Well, what of it?" he asked, attempting, without success, to hide his annoyance. "I sincerely hope you're not taking this seriously."

    "Neither seriously nor frivolously," Vance sighed; "but with an open mind, old dear. The epistle has possibilities, don't y' know."

    "For Heaven's sake, Vance!" Markham protested. "We get letters like that every day. Scores of them. If we paid any attention to them we'd have time for nothing else. The letter-writing habit of professional trouble-makers—But I don't have to go into that with you: you're too good a psychologist."

    Vance nodded with unwonted seriousness.

    "Yes, yes—of course. The epistol'ry complex. A combination of futile egomania, cowardice and Sadism—I'm familiar with the formula. But, really, y' know, I'm not convinced that this particular letter falls in that categ'ry."

    Markham glanced up.

    "You really think it's an honest expression of concern based on inside knowledge?"

    "Oh, no. On the contr'ry." Vance regarded his cigarette meditatively. "It goes deeper than that. If it were a sincere letter it would be less verbose and more to the point. Its very verbosity and its stilted phraseology indicate an ulterior motive: there's too much thought behind it. . . . And there are sinister implications in it—an atmosphere of abnormal reasoning—a genuine note of cruel tragedy, as if a fiend of some kind were plotting and chuckling at the same time. . . . I don't like it, Markham—I don't at all like it."

    Markham regarded Vance with considerable surprise. He started to say something, but, instead, picked up the letter and read it again, more carefully this time. When he had finished he shook his head slowly.

    "No, Vance," he protested mildly. "The saddest days of the year have affected your imagination. This letter is merely the outburst of some hysterical woman similarly affected."

    "There are a few somewhat feminine touches in it—eh, what?" Vance spoke languidly. "I noticed that. But the general tone of the letter is not one that points to hallucinations."

    Markham waved his hand in a deprecatory gesture and drew on his cigar a while in silence. At length he asked:

    "You know the Llewellyns personally?"

    "I've met Lynn Llewellyn once;—just a curs'ry introduction—and I've seen him at the Casino a number of times. The usual wild type of pampered darling whose mater holds the purse strings. And, of course, I know Kinkaid. Every one knows Richard Kinkaid but the police and the District Attorney's office." Vance shot Markham a waggish look. "But you're quite right in ignoring his existence and refusing to close his gilded den of sin. It's really run pretty straight, and only people who can afford it go there. My word! Imagine the naïveté of a mind that thinks gambling can be stopped by laws and raids! . . . The Casino is a delightful place, Markham—quite correct and all that sort of thing. You'd enjoy it immensely." Vance sighed dolefully. "If only you weren't the D. A.! Sad . . . sad. . . ."

    Markham shifted uneasily in his chair, and gave Vance a withering look followed by an indulgent smile.

    "I may go there some time—after the next election perhaps," he returned. "Do you know any of the others mentioned in the letter?"

    "Only Morgan Bloodgood," Vance told him. "He's Kinkaid's chief croupier—his right hand, so to speak. I know him only professionally, however, though I've heard he's a friend of the Llewellyns and knew Lynn's wife when she was in musical comedy. He's a college man, a genius at figures: he majored in mathematics at Princeton, Kinkaid told me once. Held an instructorship for a year or two, and then threw in his lot with Kinkaid. Probably needed excitement—anything's preferable to the quantum theory. . . . The other prospective dramatis personæ are unknown to me. I never even saw Virginia Vale—I was abroad during her brief triumph on the stage. And old Mrs. Llewellyn's path has never crossed mine. Nor have I ever met the art-aspiring daughter, Amelia."

    "What of the relations between Kinkaid and old Mrs. Llewellyn? Do they get along as brother and sister should?"

    Vance looked up at Markham languidly.

    "I'd thought of that angle, too." He mused for a moment. "Of course, the old lady is ashamed of her wayward brother—it's quite annoyin' for a fanatical social worker to harbor a brother who's a professional gambler; and while they're outwardly civil to each other, I imagine there's internal friction, especially as the Park-Avenue house belongs to them jointly and they both live under its protectin' roof. But I don't think the old girl would carry her animosity so far as to do any plotting against Kinkaid. . . . No, no. We can't find an explanation for the letter along that line. . . ."

    At this moment Currie entered the library.

    "Pardon me, sir," he said to Vance in a troubled tone; "but there's a person on the telephone who wishes me to ask you if you intend to be at the Casino tonight—"

    "Is it a man or a woman?" Vance interrupted.

    "I—really, sir—" Currie stammered, "I couldn't say. The voice was very faint and indistinct—disguised, you might say. But the person asked me to tell you that he—or she, sir—would not say another word, but would wait on the wire for your answer."

    Vance did not speak for several moments.

    "I've rather been expecting something of the sort," he murmured finally. Then he turned to Currie. "Tell my ambiguously sexed caller that I will be there at ten o'clock."

    Markham took his cigar slowly from his mouth and looked at Vance with troubled concern.

    "You actually intend to go to the Casino because of that letter?"

    Vance nodded seriously.

    "Oh, yes—quite."