"There _were_ always some of those clouds of radon or whatever they are around, each time!" he thought. "I wonder if--" A red-hot thought brought him to his feet. "Holy cats! Maybe I've got the answer!" He jumped away from the Proxy-board without a further glance at that bank of intricate controls, and hurried down a corridor. Through the glass doors he passed, Norris could see the other operators at work. Each sat in front of his control-board, wearing his television helmet, flipping the switches with expert precision. Each was operating a mechanical Proxy somewhere on Mercury. Norris and all these other operators had been trained together when Kincaid started the Proxy Project. They had been proud of their positions, until recently. It _was_ a vitally important job, searching out the uranium so sorely needed for Earth's atomic power supply. The uranium and allied metals of Earth had years ago been ransacked and used up. There was little on Venus or Mars. Mercury had much of the precious metal in its cavernous interior. But no man, no matter how ingenious his protection, could live long enough on the terrible, semi-molten Hot Side of Mercury to conduct mining operations. That was why Kincaid had invented the Proxies. They were machines that could mine uranium where men couldn't go. Crewless ships guided by radar took the Proxies to the Base on Mercury's sunward side. From Base, each Proxy was guided by an Earth operator down into the hot fissures to find and mine the vital radioactive element. The scheme had worked well, until-- "Until we got into those deeper fissures with the Proxies," Doug Norris thought. "Seven wrecked since then! This _must_ be the answer!" Martin Kincaid looked up sharply as Norris entered his office. A look of faint dismay came on Kincaid's square, patient face. He knew that a Proxy operator wouldn't leave his board in the middle of a shift, unless there was trouble. "Go ahead and give me the bad news, Doug," he said wearily. "Proxy M-Fifty just blacked out on me, down in Fissure Four," Norris admitted. "Just like the others. But I think I know why, now!" He continued excitedly: "Mart, seven Proxies blacking out in two weeks wasn't just accident. It was done deliberately!" Kincaid stared. "You mean that Hurriman's bunch is somehow sabotaging our Project?" Doug Norris interrupted with a denial. "Not that. Hurriman and his fellow politicians merely want to get their hands on the Proxy Project, not to destroy it." "Then who did wreck our Proxies?" Kincaid demanded. Norris answered excitedly. "I believe we've run into living creatures in those depths, and they're attacking us." Kincaid grunted. "The temperature in those fissures is about four hundred degrees Centigrade, the same as Mercury's sunward side. Life can't exist in heat like that. I suggest you take a rest."