He had a head-set adjusted, and McGuire took up the other. Again the room was still, and again from the far reaches of space the dark night sent to them its quavering call. The weird shrillness cried less loudly now, and the men listened in strained silence to the go and come of that variable shriek. Musical at times as it leaped from one clear note to another, again it would merge into discordant blendings of half-tones that sent shivers of nervous reaction up the listeners' spines. "Listen," said McGuire abruptly. "Check me on this. There are two of them, one loud and one faint--right?" "Right," said Captain Blake. "Now notice the time intervals--there! The faint one stops, and the big boy cuts in immediately. No waiting; he answers quickly. He does it every time." "Well?" the captain asked. "Listen when he stops and see how long before the faint one answers. Call the loud one the ship and the faint one the station.... There! The ship is through!" There was pause; some seconds elapsed before the answer that whispered so faintly in their ears came out of the night. "You are right, sir," the operator said in corroboration of McGuire's remark. "There is that wait every time." "The ship answers at once," said McGuire; "the station only after a wait." "Meaning--?" inquired the captain. "Meaning, as I take it, that there is time required for the message to go from the ship to the station and for them to reply." "An appreciable time like that," Captain Blake exclaimed, "--with radio! Why, a few seconds, even, would carry it around the world a score of times!" Lieutenant McGuire hesitated a moment. "It happens every time," he reminded the captain: "it is no coincidence. And if that other station is out in space--another ship perhaps, relaying the messages to yet others between here and--Venus, let us say...." * * * * * He left the thought unfinished. Captain Blake was staring at him as one who beholds a fellow-man suddenly insane. But the look in his eyes changed slowly, and his lips that had been opened in remonstrance came gradually in a firm, straight line. "Crazy!" he said, but it was apparent that he was speaking as much to himself as to McGuire. "Plumb, raving crazy!... Yet that ship _did_ go straight up out of sight--an acceleration in the upper air beyond anything we know. It might be--" And he, too, stopped at the actual voicing of the wild surmise. He shook his head sharply as if to rid it of intruding, unwelcome thoughts. "Forget that!" he told McGuire, and repeated it in a less commanding tone. "Forget it, Mac: we've got to render a report to sane men, you and I. What we know will be hard enough for them to believe without any wild guesses. "That new craft is real. It has got it all over us for size and speed and potential offensive action. Who made it? Who mans it? Red Russia? Japan? That's what the brass hats will be wondering; that's what they will want to find out.