"As far as our physicists know, atomic power's possible if there's a known way to start it and control it. Earth's reserves are nearly exhausted. Oil, coal--used up almost completely. And Earth needs power plenty bad, to maintain civilization." "The other planets have fuel." "Spaceshipping's too expensive. It's prohibitive, Paula. Unless a new power source is found very soon, Earthmen may have to migrate to another world--and our civilization's so complex that that's nearly impossible. Maybe we can find the answer in Chahnn this time. It was one of the biggest cities of the Ancients." "I've never seen it," Captain Brown said. * * * * * Benson grunted. "I did, once. Years ago. Tremendous! The scientific achievements they must have had! And nobody knows what happened to the Ancients. They just vanished, and their machines kept running till they'd used up their power--and stopped. So there's no trace left. We've located the fuel chambers, but in every case they've been empty. Experiments have been made--unsuccessfully." "You still think my translation of the Harro Panel was wrong, eh?" Paula put in. "I do," Commander Benson said. "It was a variable cipher. No one else agrees with you that it was a code map." "Ever heard of a double code?" "I'm sorry," Benson said shortly. "We've settled all this. The Black Forest is impassable. We can't risk our chance of success on a wild goose chase." Beside the pilot, Garth's mouth twisted sardonically. He had an idea, now, what Carver Brown and Paula were after. The secret of the Ancients' power-source. Well, it might be found in the Black Forest. Anything might. Including the lost race of the Zarno, and.... His eyes went hard. Not yet would he let himself believe Doc Willard was still alive. The most he could hope for was an answer to that question--the tormenting problem of whether or not he had killed Willard. Lost in his absorption, he snapped out of it scarcely in time as the truck-cat skidded on slick ice. "Hard left! Sand the treads!" Instinctively his hand flashed to the right lever, releasing a sprinkling of sand that provided traction. He held it down while the pilot fought the wheel. They lurched, swung half around, and found level surface again. Through the window Garth could see a twenty-foot-wide funnel, sloping down to a black hole at the center. "What was it?" the pilot asked. "_Creethas_, the natives call 'em, but that doesn't mean much. Six-foot insects. Poisonous. They dig traps like ant-lions on Earth, pits with sloping sides. Once you skid on the ice, you slip on down to the hole at the bottom." "Dangerous?" "Not to us, in here. But we might have damaged the engine." "Keep your eyes open after this, Garth," Commander Benson said sharply. "Okay." Garth was silent. The truck-cat drove on, leading the procession.