The Thinking Machine/The Scarlet Thread

—Professor Augustus S. F. X. Van Dusen, Ph.D, LL.D., F.R.S., M.D., etc., scientist and logician—listened intently and without comment to a weird, seemingly inexplicable story. Hutchinson Hatch, reporter, was telling it. The bowed figure of the savant lay at ease in a large chair. The enormous head with its bushy yellow hair was thrown back, the thin, white fingers were pressed tip to tip and the blue eyes, narrowed to mere slits, squinted aggressively upward. The scientist was in a receptive mood.

“From the beginning, every fact you know,” he had requested.

“It's all out in the Back Bay,” the reporter explained. “There is a big apartment house there, a fashionable establishment, in a side street, just off Commonwealth Avenue. It is five stories in all, and is cut up into small suites, of two and three rooms with a bath. These suites are handsomely, even luxuriously furnished, and are occupied by people who can afford to pay big rents. Generally these are young unmarried men, although in several cases they are husband and wife. It is a house of every modern improvement, elevator service, hall boys, liveried door men, spacious corridors and all that. It has both the gas and electric systems of lighting. Tenants are at liberty to use either or both.

“A young broker, Weldon Henley, occupies one of the handsomest of these suites, being on the second floor, in front. He has met with considerable success in the Street. He is a bachelor and lives there alone. There is no personal servant. He dabbles in photography as a hobby, and is said to be remarkably expert.

“Recently there was a report that he was to be married this Winter to a beautiful Virginia girl who has been visiting Boston from time to time, a Miss Lipscomb—Charlotte Lipscomb, of Richmond. Henley has never denied or affirmed this rumor, although he has been asked about it often. Miss Lipscomb is impossible of access even when she visits Boston. Now she is in Virginia, I understand, but will return to Boston later in the season.”

The reporter paused, lighted a cigarette and leaned forward in his chair, gazing steadily into the inscrutable eyes of the scientist.

“When Henley took the suite he requested that all the electric lighting apparatus be removed from his apartments,” he went on. “He had taken a long lease of the place, and this was done. Therefore he uses only gas for lighting purposes, and he usually keeps one of his gas jets burning low all night.”

“Bad, bad for his health,” commented the scientist.

“Now comes the mystery of the affair,” the reporter went on. “It was five weeks or so ago Henley retired as usual—about midnight. He locked his door on the inside—he is positive of that—and awoke about four o'clock in the morning nearly asphyxiated by gas. He was barely able to get up and open the window to let in the fresh air. The gas jet he had left burning was out, and the suite was full of gas.”

“Accident, possibly,” said The Thinking Machine. “A draught through the apartments; a slight diminution of gas pressure; a hundred possibilities.”

“So it was presumed,” said the reporter. “Of course it would have been impossible for”

“Nothing is impossible,” said the other, tartly. “Don't say that. It annoys me exceedingly.”

“Well, then, it seems highly improbable that the door had been opened or that anyone came into the room and did this deliberately,” the newspaper man went on, with a slight smile. “So Henley said nothing about this; attributed it to accident. The next night he lighted his gas as usual, but he left it burning a little brighter. The same thing happened again.”

“Ah,” and The Thinking Machine changed his position a little. “The second time.”

“And again he awoke just in time to save himself,” said Hatch. “Still he attributed the affair to accident, and determined to avoid a recurrence of the affair by doing away with the gas at night. Then he got a small night lamp and used this for a week or more.”

“Why does he have a light at all?” asked the scientist, testily.

“I can hardly answer that,” replied Hatch. “I may say, however, that he is of a very nervous temperament, and gets up frequently during the night. He reads occasionally when he can't sleep. In addition to that he has slept with a light going all his life; it's a habit.”

“Go on.”

“One night he looked for the night lamp, but it had disappeared—at least he couldn't find it—so he lighted the gas again. The fact of the gas having twice before gone out had been dismissed as a serious possibility. Next morning at five o'clock a bell boy, passing through the hall, smelled gas and made a quick investigation. He decided it came from Henley's place, and rapped on the door. There was no answer. It ultimately developed that it was necessary to smash in the door. There on the bed they found Henley unconscious with the gas pouring into the room from the jet which he had left lighted. He was revived in the air, but for several hours was deathly sick.”

“Why was the door smashed in?” asked The Thinking Machine. “Why not unlocked?”

“It was done because Henley had firmly barred it,” Hatch explained. “He had become suspicious, I suppose, and after the second time he always barred his door and fastened every window before he went to sleep. There may have been a fear that some one used a key to enter.”

“Well?” asked the scientist. “After that?”

“Three weeks or so elapsed, bringing the affair down to this morning,” Hatch went on. “Then the same thing happened a little differently. For instance, after the third time the gas went out Henley decided to find out for himself what caused it, and so expressed himself to a few friends who knew of the mystery. Then, night after night, he lighted the gas as usual and kept watch. It was never disturbed during all that time, burning steadily all night. What sleep he got was in daytime.

“Last night Henley lay awake for a time; then, exhausted and tired, fell asleep. This morning early he awoke; the room was filled with gas again. In some way my city editor heard of it and asked me to look into the mystery.”

That was all. The two men were silent for a long time, and finally The Thinking Machine turned to the reporter.

“Does anyone else in the house keep gas going all night?” he asked.

“I don't know,” was the reply. “Most of them, I know, use electricity.”

“Nobody else has been overcome as he has been?”

“No. Plumbers have minutely examined the lighting system all over the house and found nothing wrong.”

“Does the gas in the house all come through the same meter?”

“Yes, so the manager told me. This meter, a big one, is just off the engine room. I supposed it possible that some one shut it off there on these nights long enough to extinguish the lights all over the house, then turned it on again. That is, presuming that it was done purposely. Do you think it was an attempt to kill Henley?”

“It might be,” was the reply. “Find out for me just who in the house uses gas; also if anyone else leaves a light burning all night; also what opportunity anyone would have to get at the meter, and then something about Henley's love affair with Miss Lipscomb. Is there anyone else? If so, who? Where does he live? When you find out these things come back here.”

That afternoon at one o'clock Hatch returned to the apartments of The Thinking Machine, with excitement plainly apparent on his face.

“Well?” asked the scientist.

“A French girl, Louise Regnier, employed as a maid by Mrs. Standing in the house, was found dead in her room on the third floor today at noon,” Hatch explained quickly. “It looks like suicide.”

“How?” asked The Thinking Machine.

“The people who employed her—husband and wife—have been away for a couple of days,” Hatch rushed on. “She was in the suite alone. This noon she had not appeared, there was an odor of gas and the door was broken in. Then she was found dead.”

“With the gas turned on?”

“With the gas turned on. She was asphyxiated.”

“Dear me, dear me,” exclaimed the scientist. He arose and took up his hat. “Let's go and see what this is all about.”

Professor Van Dusen and Hatch arrived at the apartment house they had been preceded by the Medical Examiner and the police. Detective Mallory, whom both knew, was moving about in the apartment where the girl had been found dead. The body had been removed and a telegram sent to her employers in New York.

“Too late,” said Mallory, as they entered.

“What was it, Mr. Mallory?” asked the scientist.

“Suicide,” was the reply. “No question of it. It happened in this room,” and he led the way into the third room of the suite. “The maid, Miss Regnier, occupied this, and was here alone last night. Mr. and Mrs. Standing, her employers, have gone to New York for a few days. She was left alone, and killed herself.”

Without further questioning The Thinking Machine went over to the bed, from which the girl's body had been taken, and, stooping beside it, picked up a book. It was a novel by “The Duchess.” He examined this critically, then, standing on a chair, he examined the gas jet. This done, he stepped down and went to the window of the little room. Finally The Thinking Machine turned to the detective.

“Just how much was the gas turned on?” he asked.

“Turned on full,” was the reply.

“Were both the doors of the room closed?”

“Both, yes.”

“Any cotton, or cloth, or anything of the sort stuffed in the cracks of the window?”

“No. It's a tight-fitting window, anyway. Are you trying to make a mystery out of this?”

“Cracks in the doors stuffed?” The Thinking Machine went on.

“No.” There was a smile about the detective's lips.

The Thinking Machine, on his knees, examined the bottom of one of the doors, that which led into the hall. The lock of this door had been broken when employees burst into the room. Having satisfied himself here and at the bottom of the other door, which connected with the bedroom adjoining, The Thinking Machine again climbed on a chair and examined the doors at the top.

“Both transoms closed, I suppose?” he asked.

“Yes,” was the reply. “You can't make anything but suicide out of it,” explained the detective. “The Medical Examiner has given that as his opinion—and everything I find indicates it.”

“All right,” broke in The Thinking Machine abruptly. “Don't let us keep you.”

After awhile Detective Mallory went away. Hatch and the scientist went down to the office floor, where they saw the manager. He seemed to be greatly distressed, but was willing to do anything he could in the matter.

“Is your night engineer perfectly trustworthy?” asked The Thinking Machine.

“Perfectly,” was the reply. “One of the best and most reliable men I ever met. Alert and wide-awake.”

“Can I see him a moment? The night man, I mean?”

“Certainly,” was the reply. “He's downstairs. He sleeps there. He's probably up by this time. He sleeps usually till one o'clock in the daytime, being up all night.”

“Do you supply gas for your tenants?”

“Both gas and electricity are included in the rent of the suites. Tenants may use one or both.”

“And the gas all comes through one meter?”

“Yes, one meter. It's just off the engine room.”

“I suppose there's no way of telling just who in the house uses gas?”

“No. Some do and some don't. I don't know.”

This was what Hatch had told the scientist. Now together they went to the basement, and there met the night engineer, Charles Burlingame, a tall, powerful, clean-cut man, of alert manner and positive speech. He gazed with a little amusement at the slender, almost childish figure of The Thinking Machine and the grotesquely large head.

“You are in the engine room or near it all night every night?” began The Thinking Machine.

“I haven't missed a night in four years,” was the reply.

“Anybody ever come here to see you at night?”

“Never. It's against the rules.”

“The manager or a hall boy?”

“Never.”

“In the last two months?” The Thinking Machine persisted.

“Not in the last two years,” was the positive reply. “I go on duty every night at seven o'clock, and I am on duty until seven in the morning. I don't believe I've seen anybody in the basement here with me between those hours for a year at least.”

The Thinking Machine was squinting steadily into the eyes of the engineer, and for a time both were silent. Hatch moved about the scrupulously clean engine room and nodded to the day engineer, who sat leaning back against the wall. Directly in front of him was the steam gauge.

“Have you a fireman?” was The Thinking Machine's next question.

“No. I fire myself,” said the night man. “Here's the coal,” and he indicated a bin within half a dozen feet of the mouth of the boiler.

“I don't suppose you ever had occasion to handle the gas meter?” insisted The Thinking Machine.

“Never touched it in my life,” said the other. “I don't know anything about meters, anyway.”

“And you never drop off to sleep at night for a few minutes when you get lonely? Doze, I mean?”

The engineer grinned good-naturedly.

“Never had any desire to, and besides I wouldn't have the chance,” he explained. “There's a time check here,”—and he indicated it. “I have to punch that every half hour all night to prove that I have been awake.”

“Dear me, dear me,” exclaimed The Thinking Machine, irritably. He went over and examined the time check—a revolving paper disk with hours marked on it, made to move by the action of a clock, the face of which showed in the middle.

“Besides there's the steam gauge to watch,” went on the engineer. “No engineer would dare go to sleep. There might be an explosion.”

“Do you know Mr. Weldon Henley?” suddenly asked The Thinking Machine.

“Who?” asked Burlingame.

“Weldon Henley?”

“No-o,” was the slow response. “Never heard of him. Who is he?”

“One of the tenants, on the second floor, I think.”

“Lord, I don't know any of the tenants. What about him?”

“When does the inspector come here to read the meter?”

“I never saw him. I presume in daytime, eh Bill?” and he turned to the day engineer.

“Always in the daytime—usually about noon,” said Bill from his corner.

“Any other entrance to the basement except this way—and you could see anyone coming here this way I suppose?”

“Sure I could see 'em. There's no other entrance to the cellar except the coal hole in the sidewalk in front.”

“Two big electric lights in front of the building, aren't there?”

“Yes. They go all night.”

A slightly puzzled expression crept into the eyes of The Thinking Machine. Hatch knew from the persistency of the questions that he was not satisfied; yet he was not able to fathom or to understand all the queries. In some way they had to do with the possibility of some one having access to the meter.

“Where do you usually sit at night here?” was the next question.

“Over there where Bill's sitting. I always sit there.”

The Thinking Machine crossed the room to Bill, a typical, grimy-handed man of his class.

“May I sit there a moment?” he asked.

Bill arose lazily, and The Thinking Machine sank down into the chair. From this point he could see plainly through the opening into the basement proper—there was no door—the gas meter of enormous proportions through which all the gas in the house passed. An electric light in the door made it bright as daylight. The Thinking Machine noted these things, arose, nodded his thanks to the two men and, still with the puzzled expression on his face, led the way upstairs. There the manager was still in his office.

“I presume you examine and know that the time check in the engineer's room is properly punched every half-hour during the night?” he asked.

“Yes. I examine the dial every day—have them here, in fact, each with the date on it.”

“May I see them?”

Now the manager was puzzled. He produced the cards, one for each day, and for half an hour. The Thinking Machine studied them minutely. At the end of that time, when he arose and Hatch looked at him inquiringly, he saw still the perplexed expression.

After urgent solicitation, the manager admitted them to the apartments of Weldon Henley. Mr. Henley himself had gone to his office in State Street. Here The Thinking Machine did several things which aroused the curiosity of the manager, one of which was to minutely study the gas jets. Then The Thinking Machine opened one of the front windows and glanced out into the street. Below fifteen feet was the sidewalk; above was the solid front of the building, broken only by a flagpole which, properly roped, extended from the hall window of the next floor above out over the sidewalk a distance of twelve feet or so.

“Ever use that flagpole?” he asked the manager.

“Rarely,” said the manager. “On holidays sometimes—Fourth of July and such times. We have a big flag for it.”

From the apartments The Thinking Machine led the way to the hall, up the stairs and to the flagpole. Leaning out of this window, he looked down toward the window of the apartments he had just left. Then he inspected the rope of the flagpole, drawing it through his slender hands slowly and carefully. At last he picked off a slender thread of scarlet and examined it.

“Ah,” he exclaimed. Then to Hatch: “Let's go, Mr. Hatch. Thank you,” this last to the manager, who had been a puzzled witness.

Once on the street, side by side with The Thinking Machine, Hatch was bursting with questions, but he didn't ask them. He knew it would be useless. At last The Thinking Machine broke the silence.

“That girl, Miss Regnier, was murdered,” he said suddenly, positively. “There have been four attempts to murder Henley.”

“How?” asked Hatch, startled.

“By a scheme so simple that neither you nor I nor the police have ever heard of it being employed,” was the astonishing reply. “It is perfectly horrible in its simplicity.”

“What was it?” Hatch insisted, eagerly.

“It would be futile to discuss that now,” was the rejoinder. “There has been murder. We know how. Now the question is—who? What person would have a motive to kill Henley?”

was a pause as they walked on.

“Where are we going?” asked Hatch finally.

“Come up to my place and let's consider this matter a bit further,” replied The Thinking Machine.

Not another word was spoken by either until half an hour later, in the small laboratory. For a long time the scientist was thoughtful—deeply thoughtful. Once he took down a volume from a shelf and Hatch glanced at the title. It was “Gases: Their Properties.” After awhile he returned this to the shelf and took down another, on which the reporter caught the title, “Anatomy.”

“Now, Mr. Hatch,” said The Thinking Machine in his perpetually crabbed voice, “we have a most remarkable riddle. It gains this remarkable aspect from its very simplicity. It is not, however, necessary to go into that now. I will make it clear to you when we know the motives.

“As a general rule, the greatest crimes never come to light because the greatest criminals, their perpetrators, are too clever to be caught. Here we have what I might call a great crime committed with a subtle simplicity that is wholly disarming, and a greater crime even than this was planned. This was to murder Weldon Henley. The first thing for you to do is to see Mr. Henley and warn him of his danger. Asphyxiation will not be attempted again, but there is the possibility of poison, a pistol shot, a knife, anything almost. As a matter of fact, he is in great peril.

“Superficially, the death of Miss Regnier, the maid, looks to be suicide. Instead it is the fruition of a plan which has been tried time and again against Henley. There is a possibility that Miss Regnier was not an intentional victim of the plot, but the fact remains that she was murdered. Why? Find the motive for the plot to murder Mr. Henley and you will know why.”

The Thinking Machine reached over to the shelf, took a book, looked at it a moment, then went on:

“The first question to determine positively is: Who hated Weldon Henley sufficiently to desire his death? You say he is a successful man in the Street. Therefore there is a possibility that some enemy there is at the bottom of the affair, yet it seems hardly probable. If by his operations Mr. Henley ever happened to wreck another man's fortune find this man and find out all about him. He may be the man. There will be innumerable questions arising from this line of inquiry to a man of your resources. Leave none of them unanswered.

“On the other hand there is Henley's love affair. Had he a rival who might desire his death? Had he any rival? If so, find out all about him. He may be the man who planned all this. Here, too, there will be questions arising which demand answers. Answer then—all of them—fully and clearly before you see me again.

“Was Henley ever a party to a liason [sic] of any kind? Find that out, too. A vengeful woman or a discarded sweetheart of a vengeful woman, you know, will go to any extreme. The rumor of his engagement to Miss—Miss”

“Miss Lipscomb,” Hatch supplied.

“The rumor of his engagement to Miss Lipscomb might have caused a woman whom he had once been interested in or who was once interested in him to attempt his life. The subtler murders—that is, the ones which are most attractive as problems—are nearly always the work of a cunning woman. I know nothing about women myself,” he hastened to explain; “But Lombroso has taken that attitude. Therefore, see if there is a woman.”

Most of these points Hatch had previously seen—seen with the unerring eye of a clever newspaper reporter—yet there were several which had not occurred to him. He nodded his understanding.

“Now the center of the affair, of course,” The Thinking Machine continued, “is the apartment house where Henley lives. The person who attempted his life either lives there of has ready access to the place, and frequently spends the night there. This is a vital question for you to answer. I am leaving all this to you because you know better how to do these things than I do. That's all, I think. When these things are all learned come back to me.”

The Thinking Machine arose as if the interview were at an end, and Hatch also arose, reluctantly. An idea was beginning to dawn in his mind.

“Does there occur to you that there is any connection whatever between Henley and Miss Regnier?” he asked.

“It is possible,” was the reply. “I had thought of that. If there is a connection it is not apparent yet.”

“Then how—how was it she—she was killed, or killed herself, whichever may be true, and”

“The attempt to kill Henley killed her. That's all I can say now.”

“That all?” asked Hatch, after a pause.

“No. Warn Mr. Henley immediately that he is in grave danger. Remember the person who has planned this will probably go to any extreme. I don't know Mr. Henley, of course, but from the fact that he always had a light at night I gather that he is a timid sort of man—not necessarily a coward, but a man lacking in stamina—therefore, one who might better disappear for a week or so until the mystery is cleared up. Above all, impress upon him the importance of the warning.”

The Thinking Machine opened his pocketbook and took from it the scarlet thread which he had picked from the rope of the flagpole.

“Here, I believe, is the real clew to the problem,” he explained to Hatch. “What does it seem to be?”

Hatch examined it closely.

“I should say a strand from a Turkish bath robe,” was his final judgment.

“Possibly. Ask some cloth expert what he makes of it, then if it sounds promising look into it. Find out if by any possibility it can be any part of any garment worn by any person in the apartment house.”

“But it's so slight” Hatch began.

“I know,” the other interrupted, tartly. “It's slight, but I believe it is a part of the wearing apparel of the person, man or woman, who has four times attempted to kill Mr. Henley and who did kill the girl. Therefore, it is important.”

Hatch looked at him quickly.

“Well, how—in what manner—did it come where you found it?”

“Simple enough,” said the scientist. “It is a wonder that there were not more pieces of it—that's all.”

Perplexed by his instructions, but confident of results, Hatch left The Thinking Machine. What possible connection could this tiny bit of scarlet thread, found on a flagpole, have with one shutting off the gas in Henley's rooms? How did anyone go into Henley's rooms to shut off the gas? How was it Miss Regnier was dead? What was the manner of her death?

A cloth expert in a great department store turned his knowledge on the tiny bit of scarlet for the illumination of Hatch, but he could go no further than to say that it seemed to be part of a Turkish bath robe.

“Man or woman's?” asked Hatch.

“The material from which bath robes are made is the same for both men and women,” was the reply. “I can say nothing else. Of course there's not enough of it to even guess at the pattern of the robe.”

Then Hatch went to the financial district and was ushered into the office of Weldon Henley, a slender, handsome man of thirty-two or three years, pallid of face and nervous in manner. He still showed the effect of the gas poisoning, and there was even a trace of a furtive fear—fear of something, he himself didn't know what—in his actions.

Henley talked freely to the newspaper man of certain things, but of other things he was resentfully reticent. He admitted his engagement to Miss Lipscomb, and finally even admitted that Miss Lipscomb's hand had been sought by another man, Regnault Cabell, formerly of Virginia.

“Could you give me his address?” asked Hatch.

“He lives in the same apartment house with me—two floors above,” was the reply.

Hatch was startled; startled more than he would have cared to admit.

“Are you on friendly terms with him?” he asked.

“Certainly,” said Henley. “I won't say anything further about this matter. It would be unwise for obvious reasons.”

“I suppose you consider that this turning on of the gas was an attempt on your life?”

“I can't suppose anything else.”

Hatch studied the pallid face closely as he asked the next question.

“Do you know Miss Regnier was found dead today?”

“Dead?” exclaimed the other, and he arose. “Who—what—who is she?”

It seemed a distinct effort for him to regain control of himself.

The reporter detailed then the circumstances of the finding of the girl's body, and the broker listened without comment. From that time forward all the reporter's questions were either parried or else met with a flat refusal to answer. Finally Hatch repeated to him the warning which he had from The Thinking Machine, and feeling that he had accomplished little, went away.

At eight o'clock that night—a night of complete darkness—Henley was found unconscious, lying in a little used walk in the Common. There was a bullet hole through his left shoulder, and he was bleeding profusely. He was removed to the hospital, where he regained consciousness for just a moment.

“Who shot you?” he was asked.

“None of your business,” he replied, and lapsed into unconsciousness.

unaware of this latest attempt on the life of the broker, Hutchinson Hatch steadily pursued his investigations. They finally led him to an intimate friend of Regnault Cabell. The young Southerner had apartments on the fourth floor of the big house off Commonwealth Avenue, directly over those Henley occupied, but two flights higher up. This friend was a figure in the social set of the Back Bay. He talked to Hatch freely of Cabell.

“He's a good fellow,” he explained, “one of the best I ever met, and comes of one of the best families Virginia ever had—a true F. F. V. He's pretty quick tempered and all that, but an excellent chap, and everywhere he has gone here he has made friends.”

“He used to be in love with Miss Lipscomb of Virginia, didn't he?” asked Hatch, casually.

“Used to be?” the other repeated with a laugh. “He is in love with her. But recently he understood that she was engaged to Weldon Henley, a broker—you may have heard of him?—and that, I suppose, has dampened his ardor considerably. As a matter of fact, Cabell took the thing to heart. He used to know Miss Lipscomb in Virginia—she comes from another famous family there—and he seemed to think he had a prior claim on her.”

Hatch heard all these things as any man might listen to gossip, but each additional fact was sinking into his mind, and each additional fact led his suspicions on deeper into the channel they had chosen.

“Cabell is pretty well to do,” his informant went on, “not rich as we count riches in the North, but pretty well to do, and I believe he came to Boston because Miss Lipscomb spent so much of her time here. She is a beautiful young woman of twenty-two and extremely popular in the social world everywhere, particularly in Boston. Then there was the additional fact that Henley was here.”

“No chance at all for Cabell?” Hatch suggested.

“Not the slightest,” was the reply. “Yet despite the heartbreak he had, he was the first to congratulate Henley on winning her love. And he meant it, too.”

“What's his attitude toward Henley now?” asked Hatch. His voice was calm, but there was an underlying tense note imperceptible to the other.

“They meet and speak and move in the same set. There's no love lost on either side, I don't suppose, but there is no trace of any ill feeling.”

“Cabell doesn't happen to be a vindictive sort of man?”

“Vindictive?” and the other laughed. “No. He's like a big boy, forgiving, and all that; hot-tempered, though. I could imagine him in a fit of anger making a personal matter of it with Henley, but I don't think he ever did.”

The mind of the newspaper man was rapidly focusing on one point; the rush of thoughts, questions and doubts silenced him for a moment. Then:

“How long has Cabell been in Boston?”

“Seven or eight months—that is, he has had apartments here for that long—but he has made several visits South. I suppose it's South. He has a trick of dropping out of sight occasionally. I understand that he intends to go South for good very soon. If I'm not mistaken, he is trying now to rent his suite.”

Hatch looked suddenly at his informant; an idea of seeing Cabell and having a legitimate excuse for talking to him had occurred to him.

“I'm looking for a suite,” he volunteered at last. “I wonder if you would give me a card of introduction to him? We might get together on it.”

Thus it happened that half an hour later, about ten minutes past nine o'clock, Hatch was on his way to the big apartment house. In the office he saw the manager.

“Heard the news?” asked the manager.

“No,” Hatch replied. “What is it?”

“Somebody's shot Mr. Henley as he was passing through the Common early to-night.”

Hatch whistled in amazement.

“Is he dead?”

“No, but he is unconscious. The hospital doctors say it is a nasty wound, but not necessarily dangerous.”

“Who shot him? Do they know?”

“He knows, but he won't say.”

Amazed and alarmed by this latest development, an accurate fulfillment of The Thinking Machine's prophecy, Hatch stood thoughtful for a moment, then recovering his composure a little asked for Cabell.

“I don't think there's much chance of seeing him,” said the manager. “He's going away on the midnight train—going South, to Virginia.”

“Going away to-night?” Hatch gasped.

“Yes; it seems to have been rather a sudden determination. He was talking to me here half an hour or so ago, and said something about going away. While he was here the telephone boy told me that Henley had been shot; they had 'phoned from the hospital to inform us. Then Cabell seemed greatly agitated. He said he was going away to-night, if he could catch the midnight train, and now he's packing.”

“I suppose the shooting of Henley upset him considerably?” the reporter suggested.

“Yes, I guess it did,” was the reply. “They moved in the same set and belonged to the same clubs.”

The manager sent Hatch's card of introduction to Cabell's apartments. Hatch went up and was ushered into a suite identical with that of Henley's in every respect save in minor details of furnishings. Cabell stood in the middle of the floor, with his personal belongings scattered about the room; his valet, evidently a Frenchman, was busily engaged in packing.

Cabell's greeting was perfunctorily cordial; he seemed agitated. His face was flushed and from time to time he ran his fingers through his long, brown hair. He stared at Hatch in a preoccupied fashion, then they fell into conversation about the rent of the apartments.

“I'll take almost anything reasonable,” Cabell said hurriedly. “You see, I am going away to-night, rather more suddenly than I had intended, and I am anxious to get the lease off my hands. I pay two hundred dollars a month for these just as they are.”

“May I looked them over?” asked Hatch.

He passed from the front room into the next. Here, on a bed, was piled a huge lot of clothing, and the valet, with deft fingers, was brushing and folding, preparatory to packing. Cabell was directly behind him.

“Quite comfortable, you see,” he explained. “There's room enough if you are alone. Are you?”

“Oh, yes,” Hatch replied.

“This other room here,” Cabell explained, “is not in very tidy shape now. I have been out of the city for several weeks, and What's the matter?” he demanded suddenly.

Hatch had turned quickly at the words and stared at him, then recovered himself with a start.

“I beg your pardon,” he stammered. “I rather thought I saw you in town here a week or so ago—of course I didn't know you—and I was wondering if I could have been mistaken.”

“Must have been,” said the other easily. “During the time I was away a Miss, a friend of my sister's, occupied the suite. I'm afraid some of her things are here. She hasn't sent for them as yet. She occupied this room, I think; when I came back a few days ago she took another place and all her things haven't been removed.”

“I see,” remarked Hatch, casually. “I don't suppose there's any chance of her returning here unexpectedly if I should happen to take her apartments?”

“Not the slightest. She knows I am back, and thinks I am to remain. She was to send for these things.”

Hatch gazed about the room ostentatiously. Across a trunk lay a Turkish bath robe with a scarlet stripe in it. He was anxious to get hold of it, to examine it closely. But he didn't dare to, then. Together they returned to the front room.

“I rather like the place,” he said, after a pause, “but the price is”

“Just a moment,” Cabell interrupted. “Jean, before you finish packing that suit case be sure to put my bath robe in it. It's in the far room.”

Then one question was settled for Hatch. After a moment the valet returned with the bath robe, which had been in the far room. It was Cabell's bath robe. As Jean passed the reporter an end of the robe caught on a corner of the trunk, and, stopping, the reporter unfastened it. A tiny strand of thread clung to the metal; Hatch detached it and stood idly twirling it in his fingers.

“As I was saying,” he resumed, “I rather like the place, but the price is too much. Suppose you leave it in the hands of the manager of the house”

“I had intended doing that,” the Southerner interrupted.

“Well, I'll see him about it later,” Hatch added.

With a cordial, albeit pre-occupied, handshake, Cabell ushered him out. Hatch went down in the elevator with a feeling of elation; a feeling that he had accomplished something. The manager was waiting to get into the lift.

“Do you happen to remember the name of the young lady who occupied Mr. Cabell's suite while he was away?” he asked.

“Miss Austin,” said the manager, “but she's not young. She was about forty-five years old, I should judge.”

“Did Mr. Cabell have his servant Jean with him?”

“Oh, no,” said the manager. “The valet gave up the suite to Miss Austin entirely, and until Mr. Cabell returned occupied a room in the quarters we have for our own employees.”

“Was Miss Austin ailing in any way?” asked Hatch. “I saw a large number of medicine bottles upstairs.”

“I don't know what was the matter with her,” replied the manager, with a little puzzled frown. “She certainly was not a woman of sound mental balance—that is, she was eccentric, and all that. I think rather it was an act of charity for Mr. Cabell to let her have the suite in his absence. Certainly we didn't want her.”

Hatch passed out and burst in eagerly upon The Thinking Machine in his laboratory.

“Here,” he said, and triumphantly he extended the tiny scarlet strand which he had received from The Thinking Machine, and the other of the identical color which came from Cabell's bath robe. “Is that the same?”

The Thinking Machine placed them under the microscope and examined them immediately. Later he submitted them to a chemical test.

“It is the same,” he said, finally.

“Then the mystery is solved,” said Hatch, conclusively.

stared steadily into the eager, exultant eyes of the newspaper man until Hatch at last began to fear that he had been precipitate. After awhile, under close scrutiny, the reporter began to feel convinced that he had made a mistake—he didn't quite see where, but it must be there, and the exultant manner passed. The voice of The Thinking Machine was like a cold shower.

“Remember, Mr. Hatch,” he said, critically, “that unless every possible question has been considered one cannot boast of a solution. Is there any possible question lingering yet in your mind?”

The reporter silently considered that for a moment, then:

“Well, I have the main facts, anyway. There may be one or two minor questions left, but the principal ones are answered.”

“Then tell me, to the minutest detail, what you have learned, what has happened.”

Professor Van Dusen sank back in his old, familiar pose in the large arm chair and Hatch related what he had learned and what he surmised. He related, too, the peculiar circumstances surrounding the wounding of Henley, and right on down to the beginning and end of the interview with Cabell in the latter's apartments. The Thinking Machine was silent for a time, then there came a host of questions.

“Do you know where the woman—Miss Austin—is now?” was the first.

“No,” Hatch had to admit.

“Or her precise mental condition?”

“No.”

“Or her exact relationship to Cabell?”

“No.”

“Do you know, then, what the valet, Jean, knows of the affair?”

“No, not that,” said the reporter, and his face flushed under the close questioning. “He was out of the suite every night.”

“Therefore might have been the very one who turned on the gas,” the other put in testily.

“So far as I can learn, nobody could have gone into that room and turned on the gas,” said the reporter, somewhat aggressively. “Henley barred the doors and windows and kept watch, night after night.”

“Yet the moment he was exhausted and fell asleep the gas was turned on to kill him,” said The Thinking Machine; “thus we see that he was watched more closely than he watched.”

“I see what you mean now,” said Hatch, after a long pause.

“I should like to know what Henley and Cabell and the valet knew of the girl who was found dead,” The Thinking Machine suggested. “Further, I should like to know if there was a good-sized mirror—not one set in a bureau or dresser—either in Henley's room or the apartments where the girl was found. Find out this for me and—never mind. I'll go with you.”

The scientist left the room. When he returned he wore his coat and hat. Hatch arose mechanically to follow. For a block or more they walked along, neither speaking. The Thinking Machine was the first to break the silence:

“You believe Cabell is the man who attempted to kill Henley?”

“Frankly, yes,” replied the newspaper man.

“Why?”

“Because he had the motive—disappointed love.”

“How?”

“I don't know,” Hatch confessed. “The doors of the Henley suite were closed. I don't see how anybody passed them.”

“And the girl? Who killed her? How? Why?”

Disconsolately Hatch shook his head as he walked on. The Thinking Machine interpreted his silence aright.

“Don't jump at conclusions,” he advised sharply. “You were confident Cabell was to blame for this—and he might have been, I don't know yet—but you can suggest nothing to show how he did it. I have told you before that imagination is half of logic.”

At last the lights of the big apartment house where Henley lived came in sight. Hatch shrugged his shoulders. He had grave doubts—based on what he knew—whether The Thinking Machine would be able to see Cabell. It was nearly eleven o'clock and Cabell was to leave for the South at midnight.

“Is Mr. Cabell here?” asked the scientist of the elevator boy.

“Yes, just about to go, though. He won't see anyone.”

“Hand him this note,” instructed The Thinking Machine, and he scribbled something on a piece of paper. “He'll see us.”

The boy took the paper and the elevator shot up to the fourth floor. After awhile he returned.

“He'll see you,” he said.

“Is he unpacking?”

“After he read your note twice he told his valet to unpack,” the boy replied.

“Ah, I thought so,” said The Thinking Machine.

With Hatch, mystified and puzzled, following, The Thinking Machine entered the elevator to step out a second or so later on the fourth floor. As they left the car they saw the door of Cabell's apartment standing open; Cabell was in the door. Hatch traced a glimmer of anxiety in the eyes of the young man.

“Professor Van Dusen?” Cabell inquired.

“Yes,” said the scientist. “It was of the utmost importance that I should see you, otherwise I should not have come at this time of night.”

With a wave of his hand Cabell passed that detail.

“I was anxious to get away at midnight,” he explained, “but, of course, now I shan't go, in view of your note. I have ordered my valet to unpack my things, at least until to-morrow.”

The reporter and the scientist passed into the luxuriously furnished apartments. Jean, the valet, was bending over a suit case as they entered, removing some things he had been carefully placing there. He didn't look back or pay the least attention to the visitors.

“This is your valet?” asked The Thinking Machine.

“Yes,” said the young man.

“French, isn't he?”

“Yes.”

“Speak English at all?”

“Very badly,” said Cabell. “I use French when I talk to him.”

“Does he know that you are accused of murder?” asked The Thinking Machine, in a quiet, conversational tone.

The effect of the remark on Cabell was startling. He staggered back a step or so as if he had been struck in the face, and a crimson flush overspread his brow. Jean, the valet, straightened up suddenly and looked around. There was a queer expression, too, in his eyes; an expression which Hatch could not fathom.

“Murder?” gasped Cabell, at last.

“Yes, he speaks English all right,” remarked The Thinking Machine. “Now, Mr. Cabell, will you please tell me just who Miss Austin is, and where she is, and her mental condition? Believe me, it may save you a great deal of trouble. What I said in the note is not exaggerated.”

The young man turned suddenly and began to pace back and forth across the room. After a few minutes he paused before The Thinking Machine, who stood impatiently waiting for an answer.

“I'll tell you, yes,” said Cabell, firmly. “Miss Austin is a middle-aged woman whom my sister befriended several times—was, in fact, my sister's governess when she was a child. Of late years she has not been wholly right mentally, and has suffered a great deal of privation. I had about concluded arrangements to put her in a private sanitarium. I permitted her to remain in these rooms in my absence, South. I did not take Jean—he lived in the quarters of the other employees of the place, and gave the apartment entirely to Miss Austin. It was simply an act of charity.”

“What was the cause of your sudden determination to go South to-night?” asked the scientist.

“I won't answer that question,” was the sullen reply.

There was a long, tense silence. Jean, the valet, came and went several times.

“How long has Miss Austin known Mr. Henley?”

“Presumably since she has been in these apartments,” was the reply.

“Are you sure you are not Miss Austin?” demanded the scientist.

The question was almost staggering, not only to Cabell, but to Hatch. Suddenly, with flaming face, the young Southerner leaped forward as if to strike down The Thinking Machine.

“That won't do any good,” said the scientist, coldly. “Are you sure you are not Miss Austin?” he repeated.

“Certainly I am not Miss Austin,” responded Cabell, fiercely.

“Have you a mirror in these apartments about twelve inches by twelve inches?” asked The Thinking Machine, irrelevantly.

“I— I don't know,” stammered the young man. “I—have we, Jean?”

“Oui,” replied the valet.

“Yes,” snapped The Thinking Machine. “Talk English, please. May I see it?”

The valet, without a word but with a sullen glance at the questioner, turned and left the room. He returned after a moment with the mirror. The Thinking Machine carefully examined the frame, top and bottom and on both sides. At last he looked up; again the valet was bending over a suit case.

“Do you use gas in these apartments?” the scientist asked suddenly.

“No,” was the bewildered response. “What is all this, anyway?”

Without answering, The Thinking Machine drew a chair up under the chandelier where the gas and electric fixtures were and began to finger the gas tips. After awhile he climbed down and passed into the next room, with Hatch and Cabell, both hopelessly mystified, following. There the scientist went through the same process of fingering the gas jets. Finally, one of the gas tips came out in his hand.

“Ah,” he exclaimed, suddenly, and Hatch knew the note of triumph in it. The jet from which the tip came was just on a level with his shoulder, set between a dressing table and a window. He leaned over and squinted at the gas pipe closely. Then he returned to the room where the valet was.

“Now, Jean,” he began, in an even, calm voice, “please tell me if you did or did not kill Miss Regnier purposely?”

“I don't know what you mean,” said the servant sullenly, angrily, as he turned on the scientist.

“You speak very good English now,” was The Thinking Machine's terse comment. “Mr. Hatch, lock the door and use this 'phone to call the police.”

Hatch turned to do as he was bid and saw a flash of steel in young Cabell's hand, which was drawn suddenly from a hip pocket. It was a revolver. The weapon glittered in the light, and Hatch flung himself forward. There was a sharp report, and a bullet was buried in the floor.

came a fierce, hard fight for possession of the revolver. It ended with the weapon in Hatch's hand, and both he and Cabell blowing from the effort they had expended. Jean, the valet, had turned at the sound of the shot and started toward the door leading into the hall. The Thinking Machine had stepped in front of him, and now stood there with his back to the door. Physically he would have been a child in the hands of the valet, yet there was a look in his eyes which stopped him.

“Now, Mr. Hatch,” said the scientist quietly, a touch of irony in his voice, “hand me the revolver, then 'phone for Detective Mallory to come here immediately. Tell him we have a murderer—and if he can't come at once get some other detective whom you know.”

“Murderer!” gasped Cabell.

Uncontrollable rage was blazing in the eyes of the valet, and he made as if to throw The Thinking Machine aside, despite the revolver, when Hatch was at the telephone. As Jean started forward, however, Cabell stopped him with a quick, stern gesture. Suddenly the young Southerner turned on The Thinking Machine; but it was with a question.

“What does it all mean?” he asked, bewildered.

“It means that that man there,” and The Thinking Machine indicated the valet by a nod of his head, “is a murderer—that he killed Louise Regnier; that he shot Welden Henley on Boston Common, and that, with the aid of Miss Regnier, he had four times previously attempted to kill Mr. Henley. Is he coming, Mr. Hatch?”

“Yes,” was the reply. “He says he'll be here directly.”

“Do you deny it?” demanded The Thinking Machine of the valet.

“I've done nothing,” said the valet sullenly. “I'm going out of here.”

Like an infuriated animal he rushed forward. Hatch and Cabell seized him and bore him to the floor. There, after a frantic struggle, he was bound and the other three men sat down to wait for Detective Mallory. Cabell sank back in his chair with a perplexed frown on his face. From time to time he glanced at Jean. The flush of anger which had been on the valet's face was gone now; instead there was the pallor of fear.

“Won't you tell us?” pleaded Cabell impatiently.

“When Detective Mallory comes and takes his prisoner,” said The Thinking Machine.

Ten minutes later they heard a quick step in the hall outside and Hatch opened the door. Detective Mallory entered and looked from one to another inquiringly.

“That's your prisoner, Mr. Mallory,” said the scientist, coldly. “I charge him with the murder of Miss Regnier, whom you were so confident committed suicide; I charge him with five attempts on the life of Weldon Henley, four times by gas poisoning, in which Miss Regnier was his accomplice, and once by shooting. He is the man who shot Mr. Henley.”

The Thinking Machine arose and walked over to the prostate man, handing the revolver to Hatch. He glared down at Jean fiercely.

“Will you tell how you did it or shall I?” he demanded.

His answer was a sullen, defiant glare. He turned and picked up the square mirror which the valet had produced previously.

“That's where the screw was, isn't it?” he asked, as he indicated a small hole in the frame of the mirror. Jean stared at it and his head sank forward hopelessly. “And this is the bath robe you wore, isn't it?” he demanded again, and from the suit case he pulled out the garment with the scarlet stripe.

“I guess you got me all right,” was the sullen reply.

“It might be better for you if you told the story then?” suggested The Thinking Machine.

“You know so much about it, tell it yourself.”

“Very well,” was the calm rejoinder. “I will. If I make any mistake you will correct me.”

For a long time no one spoke. The Thinking Machine had dropped back into a chair and was staring through his thick glasses at the ceiling; his finger tips were pressed tightly together. At last he began:

“There are certain trivial gaps which only the imagination can supply until the matter is gone into more fully. I should have supplied these myself, but the arrest of this man, Jean, was precipitated by the attempted hurried departure of Mr. Cabell for the South to-night, and I did not have time to go into the case to the fullest extent.

“Thus, we begin with the fact that there were several clever attempts made to murder Mr. Henley. This was by putting out the gas which he habitually left burning in his room. It happened four times in all; thus proving that it was an attempt to kill him. If it had been only once it might have been accident, even twice it might have been accident, but the same accident does not happen four times at the same time of night.

“Mr. Henley finally grew to regard the strange extinguishing of the gas as an effort to kill him, and carefully locked and barred his door and windows each night. He believed that some one came into his apartments and put out the light, leaving the gas flow. This, of course, was not true. Yet the gas was put out. How? My first idea, a natural one, was that it was turned off for an instant at the meter, when the light would go out, then turned on again. This, I convinced myself, was not true. Therefore still the question—how?

“It is a fact—I don't know how widely known it is—but it is a fact that every gas light in this house might be extinguished at the same time from this room without leaving it. How? Simply by removing that gas jet tip and blowing into the gas pipe. It would not leave a jet in the building burning. It is due to the fact that the lung power is greater than the pressure of the gas in the pipes, and forces it out.

“Thus we have the method employed to extinguish the light in Mr. Henley's rooms, and all the barred and locked doors and windows would not stop it. At the same time it threatened the life of every other person in the house—that is, every other person who used gas. It was probably for this reason that the attempt was always made late at night, I should say three or four o'clock. That's when it was done, isn't it?” he asked suddenly of the valet.

Staring at The Thinking Machine in open-mouthed astonishment the valet nodded his acquiescence before he was fully aware of it.

“Yes, that's right,” The Thinking Machine resumed complacently. “This was easily found out—comparatively. The next question was how was a watch kept on Mr. Henley? It would have done no good to extinguish the gas before he was asleep, or to have turned it on when he was not in his rooms. It might have led to a speedy discovery of just how the thing was done.

“There's a spring lock on the door of Mr. Henley's apartment. Therefore it would have been impossible for anyone to peep through the keyhole. There are no cracks through which one might see. How was this watch kept? How was the plotter to satisfy himself positively of the time when Mr. Henley was asleep? How was it that the gas was put out at no time of the score or more nights Mr. Henley himself kept watch? Obviously he was watched through a window.

“No one could climb out on the window ledge and look into Mr. Henley's apartments. No one could see into that apartment from the street—that is, could see whether Mr. Henley was asleep or even in bed. They could see the light. Watch was kept with the aid offered by the flagpole, supplemented with a mirror—this mirror. A screw was driven into the frame—it has been removed now—it was swung on the flagpole rope and pulled out to the end of the pole, facing the building. To a man standing in the hall window of the third floor it offered precisely the angle necessary to reflect the interior of Mr. Henley's suite, possibly even showed him in bed through a narrow opening in the curtain. There is no shade on the windows of that suite; heavy curtains instead. Is that right?”

Again the prisoner was surprised into a mute acquiescence.

“I saw the possibility of these things, and I saw, too, that at three or four o'clock in the morning it would be perfectly possible for a person to move about the upper halls of this house without being seen. If he wore a heavy bath robe, with a hood, say, no one would recognize him even if he were seen, and besides the garb would not cause suspicion. This bath robe has a hood.

“Now, in working the mirror back and forth on the flagpole at night a tiny scarlet thread was pulled out of the robe and clung to the rope. I found this thread; later Mr. Hatch found an identical thread in these apartments. Both came from that bath robe. Plain logic shows that the person who blew down the gas pipes worked the mirror trick; the person who worked the mirror trick left the thread; the thread comes back to the bath robe—that bath robe there,” he pointed dramatically. “Thus the person who desired Henley's death was in these apartments, or had easy access to them.”

He paused for a moment and there was a tense silence. A great light was coming to Hatch, slowly but surely. The brain that had followed all this was unlimited in possibilities.

“Even before we traced the origin of the crime to this room,” went on the scientist, quietly now, “attention had been attracted here, particularly to you, Mr. Cabell. It was through the love affair, of which Miss Lipscomb was the center. Mr. Hatch learned that you and Henley had been rivals for her hand. It was that, even before this scarlet thread was found, which indicated that you might have some knowledge of the affair, directly or indirectly.

“You are not a malicious or revengeful man, Mr. Cabell. But you are hot-tempered—extremely so. You demonstrated that just now, when, angry and not understanding, but feeling that your honor was at stake, you shot a hole in the floor.”

“What?” asked Detective Mallory.

“A little accident,” explained The Thinking Machine quickly. “Not being a malicious or revengeful man, you are not the man to deliberately go ahead and make elaborate plans for the murder of Henley. In a moment of passion you might have killed him—but never deliberately as the result of premeditation. Besides you were out of town. Who was then in these apartments? Who had access to these apartments? Who might have used your bath robe? Your valet, possibly Miss Austin. Which? Now, let's see how we reached this conclusion which led to the valet.

“Miss Regnier was found dead. It was not suicide. How did I know? Because she had been reading with the gas light at its full. If she had been reading by the gas light, how was it then that it went out and suffocated her before she could arise and shut it off? Obviously she must have fallen asleep over her book and left the light burning.

“If she was in this plot to kill Henley, why did she light the jet in her room? There might have been some defect in the electric bulb in her room which she had just discovered. Therefore she lighted the gas, intending to extinguish it—turn it off entirely—later. But she fell asleep. Therefore when the valet here blew into the pipe, intending to kill Mr. Henley, he unwittingly killed the woman he loved—Miss Regnier. It was perfectly possible, meanwhile, that she did not know of the attempt to be made that particular night, although she had participated in the others, knowing that Henley had night after night sat up to watch the light in his rooms.

“The facts, as I knew them, showed no connection between Miss Regnier and this man at that time—nor any connection between Miss Regnier and Henley. It might have been that the person who blew the gas out of the pipe from these rooms knew nothing whatever of Miss Regnier, just as he didn't know who else he might have killed in the building.

“But I had her death and the manner of it. I had eliminated you, Mr. Cabell. Therefore there remained Miss Austin and the valet. Miss Austin was eccentric—insane, if you will. Would she have any motive for killing Henley? I could imagine none. Love? Probably not. Money? They had nothing in common on that ground. What? Nothing that I could see. Therefore, for the moment, I passed Miss Austin by, after asking you, Mr. Cabell, if you were Miss Austin.

“What remained? The valet. Motive? Several possible ones, one or two probable. He is French, or says he is. Miss Regnier is French. Therefore I had arrived at the conclusion that they knew each other as people of the same nationality will in a house of this sort. And remember, I had passed by Mr. Cabell and Miss Austin, so the valet was the only one left; he could use the bath robe.

“Well, the motive. Frankly that was the only difficult point in the entire problem—difficult because there were so many possibilities. And each possibility that suggested itself suggested also a woman. Jealousy? There must be a woman. Hate? Probably a woman. Attempted extortion? With the aid of a woman. No other motive which would lead to so elaborate a plot of murder would come forward. Who was the woman? Miss Regnier.

“Did Miss Regnier know Henley? Mr. Hatch had reason to believe he knew her because of his actions when informed of her death. Knew her how? People of such relatively different planes of life can know each other—or do know each other—only on one plane. Henley is a typical young man, fast, I dare say, and liberal. Perhaps, then, there had been a liason. When I saw this possibility I had my motives—all of them—jealousy, hate and possibly attempted extortion as well.

“What was more possible than Mr. Henley and Miss Regnier had been acquainted? All liasons are secret ones. Suppose she had been cast off because of the engagement to a young woman of Henley's own level? Suppose she had confided in the valet here? Do you see? Motives enough for any crime, however diabolical. The attempts on Henley's life possibly followed an attempted extortion of money. The shot which wounded Henley was fired by this man, Jean. Why? Because the woman who had cause to hate Henley was dead. Then the man? He was alive and vindictive. Henley knew who shot him, and knew why, but he'll never say it publicly. He can't afford to. It would ruin him. I think probably that's all. Do you want to add anything?” he asked the valet.

“No,” was the fierce reply. “I'm sorry I didn't kill him, that's all. It was all about as you said, though God knows how you found it out,” he added, desperately.

“Are you a Frenchman?”

“I was born in New York, but lived in France for eleven years. I first knew Louise there.”

Silence fell upon the little group. Then Hatch asked a question:

“You told me, Professor, that there would be no other attempt to kill Henley by extinguishing the gas. How did you know that?”

“Because one person—the wrong person—had been killed that way,” was the reply. “For this reason it was hardly likely that another attempt of that sort would be made. You had no intention of killing Louise Regnier, had you, Jean?”

“No, God help me, no.”

“It was all done in these apartments,” The Thinking Machine added, turning to Cabell, “at the gas jet from which I took the tip. It had been only loosely replaced and the metal was tarnished where the lips had dampened it.”

“It must take great lung power to do a thing like that,” remarked Detective Mallory.

“You would be amazed to know how easily it is done,” said the scientist. “Try it some time.”

The Thinking Machine arose and picked up his hat; Hatch did the same. Then the reporter turned to Cabell.

“Would you mind telling me why you were so anxious to get away to-night?” he asked.

“Well, no,” Cabell explained, and there was a rush of red to his face. “It's because I received a telegram from Virginia—Miss Lipscomb, in fact. Some of Henley's past had come to her knowledge and the telegram told me that the engagement was broken. On top of this came the information that Henley had been shot and—I was considerably agitated.”

The Thinking Machine and Hatch were walking along the street.

“What did you write in the note you sent to Cabell that made him start to unpack?” asked the reporter, curiously.

“There are some things that it wouldn't be well for everyone to know,” was the enigmatic response. “Perhaps it would be just as well for you to overlook this little omission.”

“Of course, of course,” replied the reporter, wonderingly.