He heard the door open and close. He was alone. Five years ago, he thought, we cracked the secret of faster-than-light travel, and since then we've built about three dozen exploration ships and sent them out among the stars to see what they could see. He stared blankly at the palms of his hand. I wonder what it was we expected to find? We found that the galaxy was big, that there were a lot of stars, not so many planets, and practically no other life--at least no intelligence to compare with ours. Then ... He jabbed a button on his intercom. "Ed Philips here. What is it Jim?" "Doc, are you sure your boys have hypo'd, couched, and hypno'd the _Leo_ crew with everything you've got?" The voice on the intercom sighed. "Jim, those guys haven't got a memory of their own. We know everything about each one of them, from the hurts he got falling off tricycles to the feel of the first girl he kissed. Those men aren't lying, Jim." "I never thought they were lying, Doc." Rothwell paused for a minute and studied the long yellow hairs that grew sparsely across the back of his hand, thickened to a dense grove at his wrist, and vanished under the sleeve of his uniform. He looked back at the intercom. "Doc, all I know is that three perfectly normal guys got on board that ship, and when it came back we found a lot of jammed instruments and three men terrified almost to the point of insanity." "Jim, if you'd seen ..." Rothwell interrupted. "I know. Five radioactive planets with the fresh scars of cobalt bombs and the remains of civilizations. Then radar screens erupting crazily with signals from a multi-thousand ship space fleet; vector computers hurriedly plotting and re-plotting the fast-moving trajectory, submitting each time an unvarying answer for the fleet's destination--our own solar system." He slapped his hand flat against the desk. "The point is, Doc, it's not much to go on, and we don't dare send another ship to check for fear of attracting attention to ourselves. If we could only be _sure_." "Jim," over the intercom, Philips' voice seemed to waver slightly, "those men honestly saw what they say. I'd stake my life on it." "All of us are, Doc." He flipped the off button. Just thirty days now, since the scout ship _Leo's_ discovery and the panicked dash for home with the warning. Not that the warning was worth much, he reflected, Earth had no space battle fleet. There had never been any reason to build one. Then, two weeks ago, Aku's trading fleet had descended from nowhere, having blundered, he said, across Earth's orbit while on a new route between two distant star clusters. When told of the impending attack, Aku immediately offered to cancel his trip and evacuate as many humans as his ships could hold, so that humanity would at least survive, somewhere in the galaxy. Earth chose to accept his offer.