It will now become necessary to glance in passing at the personal characteristics of Professor Eldridge. This man was in about his fortieth year, tall, spare, keenly intellectual in countenance, cold, possessed of an absolute reliance on the powers of science, beyond which his mental processes did not stray. His manner was distinguished by a stiff unbending formality; his expression by a glacial coldness of steel-gray eyes and a straight-line compression of thin lips; his dress by a precise and unvarying formalism, and his speech by a curious polysyllabic stiffness.

This latter idiosyncrasy would, in another, have seemed either priggish or facetiously intended. With Professor Eldridge it was merely a natural method of speech. Thus, arriving once at the stroke of the dinner hour, he replied to compliments on his punctuality by remarking:

"I have always considered punctuality a virtue when one is invited to partake of gratuitous nourishment."

Withal, his scientific attainments were not only undoubted, but so considerable as to have won for him against many odds the reputation of a great scientist. His specialty, if such it might be called, was scientific diagnosis. The exactness of scientific laws was so admirably duplicated by the exactitudes of his mind that he seemed able, by a bloodless and mechanical sympathy, to penetrate to the most obscure causes of the strangest events. It might be added that practically his only social ties were those with the Warfords, and that the only woman with whom he ever entered into conversation was Helen.

At sight of him Percy Darrow's lounging gait became accentuated to exaggeration.

"Hello, Prof!" he drawled. "On the job, I see. Good morning, Doctor," he greeted Knox. "What do you make of it?"

"I make of it that the Atlas Building will shortly be without tenants," replied the doctor; "me, for one."

Eldridge surveyed Darrow coldly through the glittering toric lenses of his glasses.

"The cause of these extraordinary phenomena is self-evident," he stated.

"You mean their nature, not their cause," replied Darrow. "In nature, they refer back to the interference with etheric and molecular vibrations. That," he added, "is a fact that every boy in the grammar-school physics class has figured out for himself. The cause is a different matter."

"I stand corrected," said Eldridge. "Such lapses in accuracy of statement are not usual with me, but may be considered as concomitant with unusual circumstances."

"Right-o!" agreed Darrow cheerfully. "Well, what about the causes?"

"That I will determine when I am satisfied that all the elements of the problem are in my hands."

"Right-o!" repeated Darrow. "Well, I'll bet you a new hat I'll land the cause before you do. Be a sport!"

"I never indulge in wagers," replied Eldridge.

"Well," said Darrow to Jack and Hallowell, "come on!"

Without waiting to see if he was followed, the young man again plunged into the black and clinging darkness.

"Get hold of my coat," his voice came to the others. "We're going to climb."

Accordingly they climbed, in silence, up many flights of stairs, through the cloying darkness. At last Darrow halted, turned sharp to the left, fumbled for a door, and entered a room.

"Simmons?" he said.

"Here!" came a voice.

"I thought you'd be on the job," said Darrow, with satisfaction. "How's your instrument? Going, eh? We are in the wireless offices," he told the others. "Sit down, if you can find chairs. We'll wait until the sun is shining brightly, love, before we really try to get down to business. In the meantime—"

"In the meantime—" repeated both Jack and Hallowell, in a breath. "Go on, my son," conceded the latter. "I bet we have the same idea."

"Well, I was going to say that I'm not in the grammar-school physics class, and I want to know what you meant by your remark to Eldridge," said Jack.

"That's my trouble," said Hallowell.

"It's simple enough," began Darrow. "We have had, first, a failure of all electricity; second, a failure of all sound; third, a failure of all light. The logical mind would therefore examine these things to see what they have in common. The answer simply jumps at you: Vibration. Electricity and light are vibrations in ether; sound is vibration in air or some solid. Therefore, whatever could absolutely stop vibration would necessarily stop electricity, light and sound."

"But," objected Jack, "if vibration were absolutely stopped, why wouldn't they all three be blotted out at once?"

"Because," explained Darrow, "the vibrations making these three phenomena are different in character. Sound is made by horizontal waves, for example, while electricity and light are made by transverse waves. Furthermore, the waves producing electricity and light differ in length. Now, it is conceivable that a condition which would interfere with horizontal waves would not interfere with transverse waves; or that a condition which would absolutely deaden waves two hundred and seventy ten-millionths of an inch long would have absolutely no effect on those one hundred and fifty-five ten-millionths of an inch long. Am I clear?"

"Sure!" came the voices of his audience.

"That much Eldridge and any other man trained in elementary science already knows. It is no secret."

"It hasn't been published," observed Hallowell grimly.

"Well, go to it! The task of the independent investigator, of which we are some, is now to discover, first, what are those conditions, and, second, what causes them. With the exception of Mr. Hallowell, we all know what this guiding power is."

"Don't get it," growled Simmons.

"Now, look here, Simmons, you are very loyal to McCarthy, for whatever reason, but your loyalty is misplaced. For one thing, your man has disappeared, and will not return. That last message scared him out. For another thing, we're going to need you in our campaign, the worst way."

"I'm from Copenhagen; you got to show me," said Simmons.

Darrow laughed softly.

"We'll show you, all right," said he. He sketched briefly for Hallowell's benefit the reasoning already followed out, and which it is therefore unnecessary to repeat here. "So now," he concluded, "we will consider this hypothesis: that these phenomena are caused by one man in control of a force capable of deadening vibrations in ether and solids within certain definite limits."

"Why do you limit it?" cried Hallowell.

"Because we have had but one manifestation at a time. If this Unknown were out really to frighten—which seems to be his intention—it would be much more effective to visit us with absolute darkness and absolute silence combined. That would be really terrifying. He has not done so. Therefore, I conclude that his power is limited in applicability."

"Isn't that a little doubtful?" spoke up Jack.

"Of course," said Darrow cheerfully. "That's where we're going to win out on this sporting proposition with our dear Brother Eldridge. He won't accept any hypothesis unless it is absolutely copper-riveted. We will."

"I think you underestimate Eldridge," spoke up Hallowell. "He's the only original think-tank in a village of horse troughs."

"I don't underestimate him one bit," countered Darrow; "but we have a head start on him with our reasoning; that's all. He's absolutely sure to come to the conclusions I have just detailed, only he'll get there a little more slowly. That's why I want you in on this thing, Hallowell."

"How's that?"

"We'll publish everything up to date and cut the ground from under him."

"What's your special grouch on Eldridge, anyway?" asked Jack.

"I like to worry him," replied Percy Darrow non-committally.

At this moment the darkness disappeared as though some one had turned a switch. The reporter, the operator and the scientist's young assistant moved involuntarily as though dodging, and blinked. Darrow shaded his eyes with one hand and proceeded as though nothing had happened.

"Here are the exclusive points of your story," he said to Hallowell, handing him a sheaf of yellow wireless forms. "I got them in McCarthy's office. They are messages from the unknown wielder of the mysterious power to his enemy, the political boss. There will be plenty who will conclude these messages to be the result of fanaticism, after the fact; that is to say, they will conclude some wireless amateur has taken advantage of natural phenomena and, by claiming himself the author of them, has attempted to use them against his enemy. Of course, the answer to that is that if the Unknown—let's call him Monsieur X—did not cause these strange things, he at least knew enough about them to predict them accurately."

"You just leave that to me," hummed Hallowell under his breath. The reporter had been glancing over the wireless forms, and his eyes were shining with delight.

"Here is the last one," said Darrow, producing a crumpled yellow paper from his pocket. "I went back after it."

"McCarthy: My patience is at an end. Your last warning will be sent you at nine thirty this morning. If you do not sail on the Celtic at noon I shall strike. You are of a stubborn and a stiff-necked generation, but I am your lord and master, and my wrath shall be visited on you. Begone, or you shall die the death."

"That bluffed him out," said Darrow, "and I don't blame him. Now, Simmons," said he, turning to the operator, who had sat in utter silence, "how about it? Are you with us, or against us?"

"How do you mean?" demanded Simmons.

"This," said Darrow sharply. "The time has passed for concealment. Every message through the ether must now reach the public. We must send messages back. The case is out of private hands; it has become important to the people. Will you agree on your honor faithfully to transmit?" He leaned forward, his indolent frame startlingly tense. "Are you afraid of McCarthy?"

"He's been good to me—it's a family matter," muttered the operator.

"Well—" Darrow arose, crossed to the operator, and whispered to him for a moment. "You see the seriousness—you are an intelligent man."

The operator turned pale.

"I hadn't thought of that," he muttered. "I hadn't thought of that. Of course I'm with you."

"I thought you would be," drawled Percy Darrow slowly. "If you hadn't decided to be, I'd have had another man put in your place. Hadn't thought of that, either, had you?"

"No, sir," replied Simmons.

"Well, I prefer you. It's no job for a quitter, and I believe you'll stick."

"I'll stick," repeated Simmons.

"Well, to work," said Darrow, lighting the cigarette he had been playing with. "Send this out, and see if you can reach Monsieur X.

"'M,'" he dictated slowly. "'Do you get this?' Repeat that until you get a reply."

Without comment the operator turned to his key. The long ripping crashes of the wireless sender followed the movements of his fingers.

"I get his 'I—I,'" he said, after a moment. "It's almighty faint."

"Good!" said Darrow. "Give him this:

"'McCarthy has disappeared. Can no longer reach him with your messages.'"

"He merely answers 'I—I,'" observed the operator.

"By the way," asked Darrow, "what is your shift, anyhow? Weren't you on at night when this thing began?"

"I'm still on at night; but Mr. McCarthy sent me a message, and asked me to stay on all this morning as a personal favor to him."

"I see. Then you're still on at night?"

"Yes, sir."

"Well, tell Monsieur X that fact, put yourself at his disposal, and tell him he'd better get all his messages to you rather than to the other operators here."

"All right."

"There's your story," said Darrow to Hallowell; "it's in those messages. The scientific aspect will probably be done by somebody for the evening papers. You better concentrate on Monsieur X's connection with McCarthy."

"Say, my friend," said Hallowell earnestly, "do you think I'm a reporter for the Scientific American or a newspaper?"

All three rose. The operator was busy crashing away at his Leyden jars.

"What next?" asked Jack.

"That depends on two things."

"Whether or not McCarthy takes the Celtic," interposed Hallowell quickly.

"And whether Monsieur X will be satisfied with his mere disappearance, if he does not take the Celtic," supplemented Darrow. "In any case, we've got to find him. He's unbalanced; he possesses an immense and disconcerting and a dangerous power; he is becoming possessed of a manie des grandeurs. You remember the phrasing of his last message? 'I am your lord and master, and my wrath shall be visited on you. Begone!' That is the language of exaltation. Exaltation is not far short of irresponsible raving."

"What possible clue—" began Jack Warford blankly.

"When a man is somewhere out in the ether there is no clue," replied
Darrow.

"Then how on earth can you hope to find him?"

"By the exercise of pure reason," said Darrow calmly.

With a final warning to Simmons as to the dissemination of any information without consulting him, Darrow left the room. Hallowell listened to this advice with unmixed satisfaction; the afternoon papers would not be able to get at his source of information. The reporter felt a slight wonder as to how Darrow had managed his ascendency over the operator. An inquiry as to that met with a shake of the head.

"I may have to ask your help in that later," was his only reply.

At the corner, after pushing through a curious crowd, the men separated. Hallowell started for the wharf; Jack Warford for home—at Darrow's request. The scientist returned to his own apartments, where he locked himself in and sat for five hours cross-legged on a divan, staring straight ahead of him, doing nothing. At the end of that time he cautiously stretched his legs, sighed, rose, and looked into the mirror.

"I guess you're hungry," he remarked to the image therein.

It was now near mid-afternoon. Percy Darrow wandered out, ate a leisurely meal at the nearest restaurant, and sauntered up the avenue. He paused at a news stand to buy an afternoon paper, glanced at the head-lines and a portion of the text, and smiled sweetly to himself. Then he betook himself by means of a bus to the Warford residence.

Helen was at home, and in the library. With her was Professor Eldridge. The men greeted each other formally. After a moment of general conversation Darrow produced the newspaper.

"I see you have your theories in print," he drawled. "Very interesting. I didn't know you'd undertaken grammar-school physics instruction."

"I know I'm going to be grateful for any sort of instruction—from anybody," interposed Helen. "I'm all in the dark."

"Like the Atlas Building," Darrow smiled at her. "Well, here's a very good exposition in words of one syllable. I'll leave you the paper. Professor, what have you concluded as to the causes?"

"They are yet to be determined."

"Pardon me," drawled Darrow, "they have been determined—or at least their controlling power."

"In what way, may I ask?" inquired Professor Eldridge formally.

"Very simply. By the exercise of a little reason. I am going to tell you, because I want you to start fairly with me; and because you'll know all about it in the morning, anyway."

"Your idea—the one you told us yesterday—is to be published?" cried
Helen, leaning forward with interest.

"The basis of it will be," replied Darrow. "Now"—he turned to Eldridge—"listen carefully; I'm not going to indulge in many explanations. Malachi McCarthy, political boss of this city, has made a personal enemy of a half-crazed or at least unbalanced man, who has in some way gained a limited power over etheric and other vibrations. This power Monsieur X, as I call him—the Unknown—has employed in fantastic manifestations designed solely for the purpose of frightening his enemy into leaving this country."

Eldridge was listening with the keenest attention, his cold gray eyes glittering frostily behind their toric lenses.

"You support your major hypothesis, I suppose?" he demand calmly.

"By wireless messages sent from Monsieur X to McCarthy, in which he predicts or appoints in advance the exact hour at which these manifestations take place."

"In advance, I understand you to say?"

"Precisely."

"The proof is as conclusive for merely prophetic ability as for power over the phenomena."

"In formal logic; not in common sense."

Eldridge reflected a moment further, removing his glasses, with the edge of which he tapped methodically the palm of his left hand. Helen had sunk back into the depths of her armchair, and was watching with immobile countenance but vividly interested eyes the progress of the duel.

"Granting for the moment your major hypothesis," Eldridge stated at last, "I follow your other essential statements. The man is unbalanced because he chooses such a method of accomplishing a simple end."

"Quite so."

"His power is limited because it has been applied to but one manifestation of etheric vibration at a time; and each manifestation has had a defined duration."

Darrow bowed. "You are the only original think-tank," he quoted
Hallowell's earlier remark.

"You are most kind to place me in possession of these additional facts," said Eldridge, resuming his glasses, "for naturally my conclusions, based on incomplete premises, could hardly be considered more than tentative. The happy accident of an acquaintance with the existence of these wireless messages and this personal enmity gave you a manifest but artificial advantage in the construction of your hypothesis."

"Did I not see you in the corridor of the Atlas Building the day of the first electrical failure?" asked Darrow.

"Certainly."

"Then you had just as much to go on as I did," drawled Darrow, half closing his eyes. The long dark lashes fell across his cheek, investing him in his most harmless and effeminate look.

"I fail to—"

"Yes, you fail, all right," interrupted Darrow. "You had all the strings in your hands, but you were a mile behind me in the solution of this mystery. I'll tell you why: it was for the same reason that you're going to fail a second time, now that once again I've put all the strings in your hands."

"I must confess I fail to gather your meaning," said Professor Eldridge coldly.

"It was for the same reason that always until his death you were inferior to dear old Doctor Schermerhorn as a scientist. You are an almost perfect thinking machine."

Darrow quite deliberately lighted a cigarette, flipped the match into the grate, and leaned back luxuriously. Professor Eldridge sat bolt upright, waiting. Helen Warford watched them both.

"You have no humanity; you have no imagination," stated Darrow at last.
"You follow the dictates of rigid science, and of logic."

"Most certainly," Eldridge agreed to this, as to a compliment.

"It takes you far," continued Darrow, "but not far enough. You observe only facts; I also observe men. You will follow only where your facts lead; I am willing to take a leap in the dark. I'll have all this matter hunted out while you are proving your first steps."

"That, I understand it, is a challenge?" demanded Eldridge, touched in his pride of the scientific diagnostician.

"That," said Percy Darrow blandly, "is a statement of fact."

"We shall see."

"Sure!" agreed Darrow. "Now, the thing to do is to find Monsieur X. I don't know whether your curiously scutellate mind has arrived at the point where it is willing to admit the existence of Monsieur X or not; but it will. The man who finds Monsieur X wins. Now, you know or can read in the morning paper every fact I have. Go to it!"

Eldridge bowed formally.

"There's one other thing," went on Darrow in a more serious tone of voice. "You have, of course, considered the logical result of this power carried to its ultimate possibility."

"Certainly," replied Eldridge coldly. "The question is superfluous."

"It is a conclusion which many scientific minds will come to, but which will escape the general public unless the surmise is published. For the present I suggest that we use our influence to keep it out of the prints."

Eldridge reflected. "You are quite right," said he; and rose to go.

After his departure Helen turned on Darrow.

"You were positively insulting!" she cried, "and in my house! How could you?"

"Helen," said Darrow, facing her squarely, "I maintained rigidly all the outer forms of politeness. That is as far as I will go anywhere with that man. My statement to him is quite just; he has no humanity."

"What do you mean? Why are you so bitter?" asked Helen, a little subdued in her anger by the young man's evident earnestness.

"You never knew Doctor Schermerhorn, did you, Helen?" he asked.

"The funny little old German? Indeed, I did! He was a dear!"

"He was one of the greatest scientists living—and he was a dear! That goes far to explain him—a gentle, wise, child-like, old man—with imagination and a Heaven-seeking soul. He picked me up as a boy, and was a father to me. I was his scientific assistant until he was killed, murdered by the foulest band of pirates. Life passes; and that is long ago."

He fell silent a moment; and the girl looked on this unprecedented betrayal of feeling with eyes at once startled and sympathetic.

"Doctor Schermerhorn," went on Darrow in his usual faintly tired, faintly cynical tone, "worked off and on for five years on a certain purely scientific discovery, the nature of which you would not understand. In conversation he told its essentials to this Eldridge. Doctor Schermerhorn fell sick of a passing illness. When he had recovered, the discovery had been completed and given to the scientific world."

"Oh!" cried Helen. "What a trick!"

"So I think. The discovery was purely theoretic and brought no particular fame or money to Eldridge. It was, as he looked at it, and as the doctor himself looked at it, merely carrying common knowledge to a conclusion. Perhaps it was; but I never forgave Eldridge for depriving the old man of the little satisfaction of the final proof. It is indicative of the whole man. He lacks humanity, and therefore imagination."

"Still, I wish you wouldn't be quite so bitter when I'm around," pleaded
Helen, "though I love your feeling for dear old Doctor Schermerhorn."

"I wish you could arrange to get out of town for a little while," urged
Darrow. "Isn't there some one you can visit?"

"Do you mean there is danger?"

"There is the potentiality of danger," Darrow amended. "I am almost confident, if pure reason can be relied on, that when the time comes I can avert the danger."

"Almost—" said Helen.

"I may have missed one of the elements of the case—though I do not think so. I can be practically certain when I telephone a man I know—or see the morning papers."

"Telephone now, then. But why 'when the time comes'? Why not now?"

Darrow arose to go to the telephone. He shook his head.

"Let Eldridge do his best. He has always succeeded—triumphantly. Now he will fail, and he will fail in the most spectacular, the most public way possible."

He lifted his eyes, usually so dreamy, so soft brown. Helen was startled at the lambent flash in their depths. He sauntered from the room. After a moment she heard his voice in conversation with the man he had called.

"Hallowell?" he said, "good luck to find you. Did our friend leave on the Celtic? No? Sure he didn't sneak off in disguise? I'll trust you to think of everything. Sure! Meet me at Simmons' wireless in half an hour."

Helen heard the click as he hung up the receiver. A moment later he lounged back into the room.

"All right," he said. "My job's done."

"Done!" echoed Helen in surprise.

"Either I'm right or I'm wrong," said Darrow. "Every element of the game is now certainly before me. If my reasoning is correct I shall receive certain proof of that fact within half an hour. If it is wrong, then I'm away off, and Eldridge's methods will win if any can."

"What is the proof? Aren't you wildly excited? Tell me!" cried Helen.

"The proof is whether or not a certain message has been received over a certain wireless," said Darrow. "I'll know soon enough. But that is not the question; can not you get out of town for a little while?"

Helen surveyed him speculatively.

"If there is no danger, I can see no reason for it," she stated at length, with decision. "If there is danger you should warn a great many others."

"But if that warning might precipitate the danger?"

"Shall I go or stay?" she demanded, ignoring the equivocation.

Darrow considered.

"Stay," he decided at last. "I'll bet more than my life that I'm right," he muttered. "Now," he continued, a trifle more briskly, "be prepared for fireworks. Unless I'm very much mistaken this little old town is going variously and duly to be stood on its head at odd times soon. That's the way I size it up. Don't be frightened; don't get caught unprepared. I think we've had the whole bag of tricks. At almost any moment we're likely to be cut off from all electricity, all sound, or all light—never more than one at a time. I imagine we shall have ample warning, but perhaps not. In any case, don't be frightened. It's harmless in itself. Better stay home nights. You can reassure your friends if you want to; but on no account get my name in this. If I am quoted, it will do incalculable harm."

"Why not tell the public that it is harmless?" demanded Helen. "Think of the anxiety, the accidents, the genuine terror it would save."

Darrow rose slowly to go. He walked quite deliberately over to Helen, and faced her for a moment in silence.

"Helen," he said impressively at last, "I have talked freely with you because I felt I could trust you. Believe me, I know the exigencies of this case better than you do; and you must obey me in what I say. I am speaking very seriously. If you allow your sympathies to act on the very limited knowledge you possess, you will probably bring about incalculable harm. We walk in safety only while we stick to the path. If you try to act in any case on what your judgment or your sympathies may advise, and without consulting me, you may cause the city, the people, and all that you know or care for to be blotted out of existence. Do you understand? Do you believe me?"

"I understand; I believe you," repeated the girl a trifle faintly.

Darrow left without further ceremony. Helen stood where he had left her on the rug, staring after him, a new expression in her eyes. She had known Percy Darrow for many years. Always she had appreciated his intellect, but deprecated what she had considered his indolence, his softness of character, his tendency to let things drift. For the first time she realized that not invariably do manners make the man.