There was a feverish restlessness in the merciless gray eyes, an unpleasant frown on his brow, as Charles Duer Carroll paused on the curb in front of a tall down town office building and stared moodily across the busy street into nothingness. Carroll was a remarkable looking young man in many ways. He was young — only thirty — and physically every line of his body expressed power, sturdiness rather than youth, force rather than grace. He was blessed too with an indomitable, uncompromising jaw, the jaw of a fighting man. The chin was square, the lips thin, avaricious perhaps, the nose slightly hooked, the cheek bones high. In general his appearance was that of a keenly alert man who is never surprised; who chooses his way and pursues it aggressively without haste, without mercy, and without mistakes.

Despite his youth — it may have been because of it — Carroll was president and active head of the great brokerage concern, the Carroll–Swayne-McPartland Company, with general offices on the fourth floor of this huge building behind him. He held that responsible position by right of being the grandson of its founder, old Nick Carroll. Upon his retirement from active business a year previously the old man, a wrinkled, venomous image of the young, had banged his desk with lusty fist and so declared it — Charlie Carroll was to be his successor. There had been heartburnings, objections, violent protests even; but the old man owned five thousand of the ten thousand shares of the company, and — Charles Duer Carroll was president.

Financially the young man was interested in the company only to the extent of owning twenty-five shares, this being a gift from old Nick and a necessary qualification for an office holder. Beyond this rather meager possession — meager at least in comparison with the holdings of other officers and stockholders of the company — young Carroll had only his salary of twenty thousand dollars a year — nothing else, for he had been exalted to this from a salary of eighteen hundred and a clerk’s desk in the general office. Here for six years old Nick Carroll had drilled the business into him, warp and woof; then had come the exaltation.

Thus it came about that a pauper, from the viewpoint of financial circles, directed the affairs of a company whose business ran into millions and tens of millions annually. If young Carroll felt that he needed advice, he did not hesitate to disregard his fellows and go straight to the fountainhead, old Carroll. And when he asked for that advice he regarded it scrupulously, minutely. At other times — in fact, as a general thing — young Carroll sailed on his own course — took the bit in his teeth and did as he pleased — leaving accrued profits to inform the various stockholders of his actions. At such times old Nick was wont to rub his skinny hands together and smile.

For months after young Carroll assumed the reins of government there had been fear of a misstep and consequent wreck in the conservative hearts of officers and stockholders, except in the case of old Carroll; then this apprehension was dissipated, leaving a residue of rankling envy. Not one man in authority would have said it was not for the best that old Nick had thrust this infusion of aggressive young blood into the staid old company; but half a dozen persons at interest could have enumerated a thousand reasons why a youth of thirty should not hold the position of president, when some older man — one of themselves — knew the business better and had been in the office longer.

Be that as it may, Charles Duer Carroll, the pauper, was president of the company. When he stepped into that position he brought with him new vigor and virility and vitality and a surly, curt, merciless method which had enabled him to achieve things. This was the young man — this Charles Duer Carroll — who stood on the curb one morning staring, glaring, across the busy street. At last he dropped a half smoked cigar, ground it to shreds on the pavement beneath a vigorous heel, and turning stared up at the building. There was a window of his office in the corner straight above him, and there was work that called. But Carroll wasn’t thinking of that particularly; he was thinking of —

He snapped his fingers impatiently and entered the building. An elevator whirled him up to the fourth floor, and he entered the large outer office of the company. The forbidding frown was still on his brow, the steeliness still in his gray eyes. Several clerks nodded respectfully as he entered; but there was no greeting in return, not even a curt time of day. He strode straight across the room to his private office without a glance either to right or left, banging the door behind him.

Over in a corner of the outer office Gordon Swayne, secretary and treasurer, was dictating letters. He glanced round with an expression of annoyance on his face at the sudden noise. “Who did that?” he demanded of his stenographer.

“It was Mr. Carroll, sir.”

“Oh!” and he resumed his dictation.

For an hour or more he continued dictating; then a letter which required the attention of President Carroll came to hand and he went into the private office. He came out after a moment and spoke to his stenographer again.

“Did Mr. Carroll go into his office this morning?”

“Yes, sir.”

Swayne turned and glanced round the outer office inquiringly. “Did you see him come out?” he inquired.

“No, sir.”

That was all. Swayne laid the letter aside for the moment and continued with the other correspondence. From time to time he glanced impatiently at the clock, thence to the door from the hall. At ten minutes past eleven the stenographer returned to her own desk, and with a worried countenance Swayne went over and spoke to a bookkeeper near the door.

“Did you see Mr. Carroll go out?” he asked. “Or do you know where he went?”

“He hasn’t gone out, sir,” replied the bookkeeper. “I saw him go into his office a couple of hours ago.”

Swayne went straight toward the private office with the evident intention of leaving the letter on the president’s desk. The door of the room was still closed. He was reaching out his hand to open it, when it was opened from within and Carroll started out. Swayne stared at him a moment in a manner nearly approaching amazement.

“Well, what is it?” demanded Carroll curtly.

“I— er — here’s something I wanted to ask you about,” Swayne explained haltingly.

Carroll glanced over the extended letter. His brows contracted and he quickly looked up at the clock.

“Did this come in the morning mail?” he demanded impatiently.

“Yes. I knew —”

“You should have called it to my attention two hours ago,” said Carroll sharply. “Answer by wire that we’ll accept the proposition.”

Swayne’s face flamed suddenly at the tone and manner. “I tried to call it to your attention two hours ago,” he explained; “but you were not in your office, nor were you out here.”

“I’ve been in my office right along,” said Carroll sharply, and he glared straight into Swayne’s eyes. “Wire immediately that we’ll accept the proposition.”

The two men stood thus face to face, eyes challenging eyes, for an instant, then simultaneously turned away. Swayne’s countenance showed not only anger but bewilderment; whatever Carroll felt was not evident. Perhaps there was more color in his face than was usually there; but it had been that way when he came out of the private office, therefore was not due to any feeling aroused by the scene with Swayne.

That afternoon Carroll caused a neat placard to be placed on the door of his private office. It said briefly:

Do not enter this room without knocking. If Mr. Carroll does not answer a knock, it is to be understood that he is not to be disturbed under any circumstances.

Swayne read it and wondered, feeling somehow that it was a direct rebuke to him; the dozen or more clerks read it and wondered, and commented upon it varyingly; two office boys read it and added their opinions. On the following day the incident was repeated with slight variations. Swayne saw Carroll enter the front door, pass through the main office, and go into the private office, closing the door behind him. Half an hour later Swayne spoke to the bookkeeper Black, to whom he had spoken the day before.

“Please hand that to Mr. Carroll in his private office,” he directed.

The bookkeeper took the slip of paper which the secretary offered, crossed the office, and rapped on Carroll’s door. After a minute he returned to Swayne, who was apparently adding a column of figures.

“Mr. Carroll doesn’t answer, sir,” explained the bookkeeper.

“You know he’s in there, don’t you?” asked Swayne blandly.

“I saw him go in a few minutes ago, yes, sir; but I didn’t intrude because of the notice on the door.”

“Oh, that’s of no consequence,” exclaimed Swayne impatiently. “This is a matter of importance. Take it into him anyway, whether he answers or not.”

Again the bookkeeper went away, and again he returned. “Mr. Carroll wasn’t in there, sir,” he explained; “and I had to leave the paper on his desk.”

“I thought you said you saw him go in?” demanded Swayne.

“I did, sir.”

“Well, he must be in there; he hasn’t come out,” insisted Swayne. “Are you sure he isn’t there?”

“Why, positive, yes, sir,” replied the bewildered bookkeeper.

Swayne was bending over the high desk intently studying the figures before him. The bookkeeper stood for a little while as if awaiting another order, then resumed his work.

“We’ll go in there together and see if he isn’t to be found,” said Swayne at last in a most matter of fact tone.

“But I just —” the bookkeeper began.

“Never mind, come along,” directed Swayne; “and don’t talk too loud,” he added in a lower tone.

Wonderingly the bookkeeper followed the secretary. Swayne himself rapped on the door. There was no answer, and finally he pushed the door open quietly. Carroll was sitting at his desk going over the morning mail. He apparently was not aware that the door had been opened, and Swayne started to close it as he and the bookkeeper withdrew.

“You were mistaken, Black,” Swayne remarked casually.

“Come in, Mr. Swayne, you and Black,” called Carroll just as the door was closing.

Swayne warned the bookkeeper to silence with one quick, comprehensive glance, then reopened the door, and they entered the private office, closing the door behind them. Swayne faced his superior calmly, defiantly almost; the bookkeeper twiddled his fingers nervously.

“Since when is it customary for employees here to disobey my orders?” demanded Carroll coldly.

“Mr. Black told me you were not here, and I came to see myself,” replied Swayne with a singular emphasis on every word.

“You see that he was mistaken, then?” demanded Carroll. “Mr. Black, we shall not require your services any longer. Mr. Swayne will give you a check immediately for what is due you. And you, Mr. Swayne, understand that if my orders are not obeyed to the letter in this office I shall be compelled to make other changes. From this time forward the door will be locked when I am in my office. That’s all.”

“But I was obeying orders when —” Black began in trepidation.

“I put my order on the door for you to obey,” interrupted Carroll. “Go write him a check, Mr. Swayne.”

Swayne and Black went out, and Swayne closed the door. Carroll had been seated as they went out; but the door had no sooner closed now than they heard the lock snap inside.

“What does it mean, Black?” Swayne inquired quietly.

“I don’t know, sir,” replied the astonished bookkeeper. “He certainly was not in that room when I was in there. And as for discharging me —”

“You are not discharged,” Swayne said impatiently, with a new note in his voice. “You are going to take a vacation of a couple of weeks, though, on full salary. Meanwhile have luncheon with me today.”

Professor Augustus S. F. X. Van Dusen — The Thinking Machine — straightened up in his chair suddenly and turned his squinting, belligerent eyes full upon his two visitors.

“Never mind your personal opinion or prejudices, Mr. Swayne,” he rebuked sharply. “If you want my assistance in this matter, I must insist that you relate the facts, and only the facts, freed of all coloring which may have been infused into them by your ill feeling toward Mr. Carroll. I understand readily enough the cause of this — this ill feeling. You are his senior in the office, and he was promoted over your head to be the president of the company, while you remained secretary and treasurer. Now give me the remainder of the facts, please.”

There was a considerable pause. A flush had slowly mounted Swayne’s face, and it was only with an obvious effort that he controlled himself. Once he looked toward Black, who had been a silent witness of the interview.

“Well, after those first two incidents,” Swayne went on at last, “the door of Mr. Carroll’s private office was always locked on the inside the moment he was left alone. Now I am not a fool, Professor Van Dusen. In my mind it stands to reason that if Mr. Carroll disappeared from that room twice when the door was left unlocked, he is gone from it practically all the time when the door is locked; therefore —”

“Opinion again,” interrupted The Thinking Machine curtly. “Facts, Mr. Swayne, facts!”

“If he isn’t gone, why does he keep the door locked?”

“Perhaps,” and the crabbed little scientist regarded him coldly — “perhaps it’s really because he is busy and doesn’t want to be interrupted. That is always possible, you know. I’m that way myself sometimes.”

“And where does he go? How does he go? And why does he go?”

“If I had to diagnose this case,” remarked The Thinking Machine almost pleasantly, “I should say it was a severe attack of idle curiosity, complicated with prejudice and suspicion.” Suddenly his whole tone, his whole manner, changed. “Has the conduct of the business of the company been all it should have been since Mr. Carroll has been in charge?” he demanded.

“Well, yes,” admitted Swayne.

“He has made money for the company?”

“Yes.”

“Perhaps increased its earnings, if anything?”

Swayne nodded reluctantly.

“Nothing is stolen?” the scientist demanded. “Nothing is missing? Nothing has gone wrong?”

Three times Swayne shook his head.

The Thinking Machine arose impatiently. “If there had been anything wrong, of course you would have gone to the police,” The Thinking Machine went on. “There being nothing wrong, you came to me. I don’t mind giving what assistance I can in instances where it works for good; but my time is valuable to the world of science, Mr. Swayne, and really I can’t be disturbed by such a trivial affair as this. If anything does go wrong, if anything does happen, you are at liberty to call again. Good day.”

The two men arose, stood staring blankly at each other for a moment, then turned to go out. Swayne’s face was crimson with anger, chagrin, at his abrupt dismissal. But at the door he turned back for one final question.

“Would you mind informing us how Mr. Carroll disappeared from his office on the two occasions when we know he did disappear, before he locked his door against us?”

“You saw him go in one door; he went out another, I suppose,” replied The Thinking Machine.

“There is only one other door,” retorted Swayne with something like triumph in his voice. “That is blocked in his office by his desk and also blocked in the stockholders’ meeting room, to which it le............