"I've told you I'll send you to prison if I can," he said. "You've risked the lives of millions of people, maintaining non-quarantined communication with an unlicensed planet. If you did rescue somebody from the ruins of the robot-colony--does it occur to you that they'd be witnesses to your unauthorized presence here?" Huyghens spun the viewer again. He stopped, switched back and forth, and found what he wanted. He muttered in satisfaction: "They did run a tunnel!" Aloud he said, "I'll worry about witnesses when I have to." He pushed aside another cupboard door. Inside it were the odds and ends a man makes use of to repair the things about his house that he never notices until they go wrong. There was an assortment of wires, transistors, bolts, and similar stray items. "What now?" asked Bordman mildly. "I'm going to try to find out if there's anybody left alive over there. I'd have checked before if I'd known the colony existed. I can't prove they're all dead, but I may prove that somebody's still alive. It's barely two weeks' journey away from here. Odd that two colonies picked spots so near!" He picked over the oddments he'd selected: "Confound it!" Bordman said. "How can you check if somebody's alive some hundreds of miles away?" Huyghens threw a switch and took down a wall-panel, exposing electronic apparatus and circuits behind. He busied himself with it. "Ever think about hunting for a castaway?" he asked over his shoulder. "Here's a planet with some tens of millions of square miles on it. You know there's a ship down. You've no idea where. You assume the survivors have power--no civilized man will be without power very long, so long as he can smelt metals!--but making a space-beacon calls for high-precision measurements and workmanship. It's not to be improvised. So what will your shipwrecked civilized man do, to guide a rescue-ship to the one or two square miles he occupies among some tens of millions on the planet?" "What?" "He's had to go primitive, to begin with," Huyghens explained. "He cooks his meat over a fire, and so on. He has to make a strictly primitive signal. It's all he can do without gauges and micrometers and special tools. But he can fill all the planet's atmosphere with a signal that searchers for him can't miss. You see?" Bordman thought irritably. He shook his head. "He'll make," said Huyghens, "a spark transmitter. He'll fix its output at the shortest frequency he can contrive, somewhere in the five-to-fifty-metre wave-band, but it will tune very broad--and it will be a plainly human signal. He'll start it broadcasting. Some of those frequencies will go all around the planet under the ionosphere. Any ship that comes in under the radio roof will pick up his signal, get a fix on it, move and get another fix, and then go straight to where the castaway is waiting placidly in a hand-braided hammock, sipping whatever sort of drink he's improvised out of the local vegetation." Bordman said grudgingly: