“Really great criminals are never found out, for the simple reason that the greatest crimes — their crimes — are never discovered,” remarked Professor Augustus S. F. X. Van Dusen positively. “There is genius in the perpetration of crime, Mr. Grayson, just as there must be in its detection, unless it is the shallow work of a bungler. In this latter case there have been instances where even the police have uncovered the truth. But the expert criminal, the man of genius — the professional, I may say — regards as perfect only that crime which does not and cannot be made to appear a crime at all; therefore one that can never involve him, nor anyone else.”

The financier, J. Morgan Grayson, regarded this wizened little man of science — The Thinking Machine — thoughtfully, through the smoke of his cigar.

“It is a strange psychological fact that the casual criminal glories in his crime beforehand, and from one to ten minutes afterward,” The Thinking Machine continued. “For instance, the man who kills for revenge wants the world to know it is his work; but at the end of ten minutes comes fear, abject terror, and then, paradoxically enough, he will seek to hide his crime and protect himself by some transparent means utterly inadequate, because of what he has said or done in the passion which preceded the act. With fear comes panic, with panic irresponsibility, and then he makes the mistake — hews a pathway which the trained mind follows from motive to a prison cell.

“These are the men who are found out. But there are men of genius, Mr. Grayson, professionally engaged in crime. We never hear of them, because they are never caught, and we never even suspect them, because they make no mistake — they are men of genius. Imagine the great brains of history turned to crime. Well, there are today brains as great as any of those which make a profession of it; there is murder and theft and robbery under our noses that we never dream of. If I, for instance, should become an active criminal, can you see —” He paused.

Grayson, with a queer expression on his face, puffed steadily at his cigar.

“I could kill you now, here in this room,” The Thinking Machine went on calmly, “and no one would ever know, never even suspect. Why not? Because I would make no mistake. In other words, I would immediately take rank with the criminals of genius who are never found out.”

It was not a boast as he said it; it was merely a statement of fact. Grayson appeared to be a little startled. Where there had been only impatient interest in his manner, there was now something else — fascination, perhaps.

“How would you kill me, for instance?” he inquired curiously.

“With anyone of a dozen poisons, with virulent germs, or even with a knife or revolver,” replied the scientist placidly. “You see, I know how to use poisons; I know how to inoculate with germs; I know how to produce a suicidal appearance perfectly with either a revolver or knife. And I never make mistakes, Mr. Grayson. In the sciences we must be exact — not approximately so, but absolutely so. We must know. It isn’t like carpentry. A carpenter may make a trivial mistake in a joint, and it will not weaken his house; but if the scientist makes one mistake the whole structure tumbles down. We must know. Knowledge is progress. We gain knowledge through observation and logic — inevitable logic. And logic tells us that while two and two make four, it is not only sometimes but all the time.”

Grayson flicked the ashes off his cigar thoughtfully, and little wrinkles appeared about his eyes as he stared into the drawn, inscrutable face of the scientist. The enormous, straw yellow head was cushioned against the chair, the squinting, watery blue eyes turned upward, and the slender white fingers at rest, tip to tip. The financier drew a long breath. “I have been informed that you were a remarkable man,” he said at last slowly. “I believe it. Quinton Fraser, the banker who gave me the letter of introduction to you, told me how you once solved a remarkable mystery, in which —”

“Yes, yes,” interrupted the scientist shortly; “the Ralston bank burglary — I remember.”

“So I came to you to enlist your aid in something which is more inexplicable than that,” Grayson went on hesitatingly. “I know that no fee I might offer would influence you; yet it is a case which —”

“State it,” interrupted The Thinking Machine again.

“It isn’t a crime — that is, a crime that can be reached by law,” Grayson hurried on — “but it has cost me millions, and —”

For one instant The Thinking Machine lowered his squint eyes to those of his visitor, then raised them again. “Millions!” he repeated. “How many?”

“Six, eight, perhaps ten,” was the reply. “Briefly, there is a leak in my office. My plans become known to others almost by the time I have perfected them. My plans are large; I have millions at stake; and the greatest secrecy is absolutely essential. For years I have been able to preserve this secrecy; but half a dozen times in the last eight weeks my plans have become known, and I have been caught. Unless you know the Street, you can’t imagine what a tremendous disadvantage it is to have some one know your next move to the minutest detail, and knowing it, defeat you at every turn.”

“No, I don’t know your world of finance, Mr. Grayson,” remarked The Thinking Machine. “Give me an instance.”

“Well, take this last case,” suggested the financier earnestly. “Briefly, without technicalities, I had planned to unload the securities of the P., Q. & X. railway, protecting myself through brokers, and force the outstanding stock down to a price where other brokers, acting for me, could buy far below the actual value. In this way I intended to get complete control of the stock. But my plans became known, and when I began to unload everything was snapped up by the opposition, with the result that instead of gaining control of the road I lost heavily. The same thing has happened, with variations, half a dozen times.”

“I presume that is strictly honest?” inquired the scientist mildly.

“Honest?” repeated Grayson. “Certainly — of course. It’s business.”

“I shall not pretend to understand all that,” said The Thinking Machine curtly. “It doesn’t seem to matter, anyway. You want to know where the leak is. Is that right?”

“Precisely.”

“Well, who is in your confidence?”

“No one, except my stenographer.”

“Of course, there is an exception. Who is he, please?”

“It’s a woman — Miss Evelyn Winthrop. She has been in my employ for six years in the same capacity — more than five years before this leak appeared — and I trust her absolutely.”

“No man knows your business?”

“No,” replied the financier grimly. “I learned years ago that no one could keep my secrets as I do — there are too many temptations — therefore I never mention my plans to anyone — never — to anyone!”

“Except your stenographer,” corrected the scientist.

“I work for days, weeks, sometimes months, perfecting plans, and it’s all in my head, not on paper — not a scratch of it,” explained Grayson. “Therefore, when I say that she is in my confidence I mean that she knows my plans only half an hour or less before the machinery is put into motion. For instance, I planned this P., Q. & X. deal. My brokers didn’t know of it; Miss Winthrop never heard of it until twenty minutes before the Stock Exchange opened for business. Then I dictated to her, as I always do, some short letters of instructions to my agents. That is all she knew of it.”

“You outlined the plan in those letters?”

“No; they merely told my brokers what to do.”

“But a shrewd person, knowing the contents of all those letters, could have learned what you intended to do?”

“Yes; but no one person knew the contents of all those letters. No one broker knew what was in the other letters — many of them were unknown to each other. Miss Winthrop and I were the only two human beings who knew all that was in them.”

The Thinking Machine sat silent for so long that Grayson began to fidget in his chair. “Who was in the room besides you and Miss Winthrop before the letters were sent?” he asked at last.

“No one,” responded Grayson emphatically. “For an hour before I dictated those letters, until at least an hour afterward, after my plans had gone to smash, no one entered that room. Only she and I work there.”

“But when she finished the letters, she went out?” insisted The Thinking Machine.

“No,” declared the financier; “she didn’t even leave her desk.”

“Or perhaps sent something out — manifolds of the letters?”

“No.”

“Or called up a friend on the telephone?” continued The Thinking Machine quietly.

“Nor that,” retorted Grayson.

“Or signaled to some one through the widow?”

“No,” said the financier again. “She finished the letters, then remained quietly at her desk, reading a book. She didn’t move for two hours.”

The Thinking Machine lowered his eyes and glared straight into those of the financier. “Some one listened at the window?” he went on after a moment.

“No. It is six stories up, fronting the street, and there is no fire escape.”

“Or the door?”

“If you knew the arrangement of my offices, you would see how utterly impossible that would be, because —”

“Nothing is impossible, Mr. Grayson,” snapped the scientist abruptly. “It might be improbable, but not impossible. Don’t say that — it annoys me exceedingly.” He was silent for a moment. Grayson stared at him blankly. “Did either you or she answer a call on the phone?”

“No one called; we called no one.”

“Any apertures — holes or cracks — in your flooring or walls or ceilings?” demanded the scientist.

“Private detectives whom I had employed looked for such an opening, and there was none,” replied Grayson.

Again The Thinking Machine was silent for a long time. Grayson lighted a fresh cigar and settled back in his chair patiently. Faint cobwebby lines began to appear on the domelike brow of the scientist, and slowly the squint eyes were narrowing.

“The letters you wrote were intercepted?” he suggested at last.

“No,” exclaimed Grayson flatly. “Those letters were sent direct to the brokers by a dozen different methods, and everyone of them had been delivered by five minutes of ten o’clock, when ‘Change begins business. The last one left me at ten minutes of ten.”

“Dear me! Dear me!” The Thinking Machine arose and paced the length of the room thrice.

“You don’t give me credit for the extraordinary precautions I have taken, particularly in this last P., Q. & X. deal,” Grayson continued. “I left positively nothing undone to insure absolute secrecy. And Miss Winthrop I know is innocent of any connection with the affair. The private detectives suspected her at first, as you do, and she was watched in and out of my office for weeks. When she was not under my eyes, she was under the eyes of men to whom I had promised an extravagant sum of money if they found the leak. She didn’t know it then, and doesn’t know it now. I am heartily ashamed of it all, because the investigation proved her absolute loyalty to me. On this last day she was directly under my eyes for two hours; and she didn’t make one movement that I didn’t note, because the thing meant millions to me. That proved beyond all question that it was no fault of hers. What could I do?”

The Thinking Machine didn’t say. He paused at a window, and for minute after minute stood motionless there, with eyes narrowed down to mere slits.

“I was on the point of discharging Miss Winthrop,” the financier went on; “but her innocence was so thoroughly proved to me by this last affair that it would have been unjust, and so —”

Suddenly the scientist turned upon his visitor. “Do you talk in your sleep?” he demanded.

“No,” was the prompt reply. “I had thought of that too. It is beyond all ordinary things, professor. Yet there is a leak that is costing me millions.”

“It comes down to this, Mr. Grayson,” The Thinking Machine informed him crabbedly enough. “If only you and Miss Winthrop knew those plans, and no one else, and they did leak, and were not deduced from other things, then either you or she permitted them to leak, intentionally or unintentionally. That is as pure logic as that two and two make four; there is no need to argue it.”

“Well, of course, I didn’t,” said Grayson.

“Then Miss Winthrop did,” declared The Thinking Machine finally, positively; “unless we credit the opposition, as you call it, with telepathic gifts hitherto unheard of. By the way, you have referred to the other side only as the opposition. Do the same men, the same clique, appear against you all the time, or is it only one man?”

“It’s a clique,” explained the financier, “with millions back of it, headed by Ralph Matthews, a young man to whom I give credit for being the prime factor against me.” His lips were set sternly.

“Why?” demanded the scientist.

“Because every time he sees me he grins,” was the reply. Grayson seemed suddenly discomfited.

The Thinking Machine went to a desk, addressed an envelop, folded a sheet of paper, placed it inside, then sealed it. At length he turned back to his visitor. “Is Miss Winthrop at your office now?”

“Yes.”

“Let us go there, then.”

A few minutes later the eminent financier ushered the eminent scientist into his private office on the Street. The only other person there was a young woman — a woman of twenty six or seven, perhaps — who turned, saw Grayson, and resumed reading. The financier motioned to a seat. Instead of sitting, however, The Thinking Machine went straight to Miss Winthrop and extended a sealed envelop to her.

“Mr. Ralph Matthews asked me to hand you this,” he said.

The young woman glanced up into his face frankly, yet with a certain timidity, took the envelop, and turned it curiously in her hand.

“Mr. Ralph Matthews,” she repeated, as if the name was a strange one. “I don’t think I know him.”

The Thinking Machine stood staring at her aggressively, insolently even, as she opened the envelop and drew out the sheet of paper. There was no expression save surprise — bewilderment, rather — to be read on her face.

“Why, it’s a blank sheet!” she remarked, puzzled.

The scientist turned away suddenly toward Grayson, who had witnessed the incident with frank astonishment in his eyes. “Your telephone a moment, please,” he requested.

“Certainly; here,” replied Grayson.

“This will do,” remarked the scientist.

He leaned forward over the desk where Miss Winthrop sat, still gazing at him in a sort of bewilderment, picked up the receiver, and held it to his ear. A few moments later he was talking to Hutchinson Hatch, reporter.

“I merely wanted to ask you to meet me at my apartments in an hour,” said the scientist. “It is very important.”

That was all. He hung up the receiver, paused for a moment to admire an exquisitely wrought silver box — a “vanity” box — on Miss Winthrop’s desk, beside the telephone, then took a seat beside Grayson and began to discourse almost pleasantly upon the prevailing meteorological conditions. Grayson merely stared; Miss Winthrop continued her reading.

Professor Augustus S. F. X. Van Dusen, distinguished scientist, and Hutchinson Hatch, newspaper reporter, were poking round among the chimney pots and other obstructions on the roof of a skyscraper. Far below them the slumber enshrouded city was spread out like a panorama, streets dotted brilliantly with arc lights, and roofs hazily visible through the mists of night. Above, the infinite blackness hung like a veil, with star points breaking through here and there.

“Here are ............