"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 a.s.sistant 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 pa.s.sed 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."