Russ was scooping up bits of soil to bring back for analysis when he saw what seemed to be a wet patch on top of the wall. As he watched, it spread until it reached the bottom. In a remarkably short time a whole section of wall was gleaming wet. A patch of damp oiliness spread over the floor. "This I've got to get a sample of," said the rusty-haired astronomer. He reached for a sampling bottle in his pocket, and at the same time the patch of wetness spread to his shoes. As Russ stepped forward, there was a sucking sound, and he lifted a thick gummy mass that was stuck to his sole. He shook his foot, set it down, and lifted the other, but it, too, was imbedded in thick slime. The stuff now was running up his ankle. "Hey!" he called out, and swung one foot vigorously to free it. More swiftly than he could move, the whole patch slid down the wall and swept around him. It was moving up his legs, as if trying to envelop him. "It's alive!" he shouted, and grabbed for the knife in his belt. In vain he tried to slash out. "It's like a giant amoeba that engulfs its food! Get it off me!" But the knife was ineffective. He fired his pistol, but the thing was just a vast wide puddle of slime, without brain, heart or organ that could be harmed. The soles of Russ's boots were already half eaten away and his socks were going fast. Some of it was touching the skin of his knees. He screamed as the stuff burned him. Burl had joined the attack with his knife, but leaped back when that proved useless. His mind raced for a way to help. Above them, Boulton was swinging the helicopter down so Russ could hoist himself out of harm's way, but time would not permit it. In another instant the mass would have Russ. Burl grabbed at the straps crossing his shoulder and swung the two oxygen tanks from his back. He snatched one from its leather holster, and pointed its nozzle at the mass of slime. He turned the stream of oxygen on, and then, taking his pistol, held its muzzle in the jet of oxygen and fired it. The roar of the gun was matched by the roar of a stream of fire that shot from the tank. Wherever the burning jet of oxygen touched, the mass shriveled and blackened. Yards and yards of amoeba seemed to writhe, hump upward in agony, and pull away. There was a ring of burned white along the ground, a sickening smell in the air, but the thing was dead. Russell Clyde grabbed the ladder as it swung toward him, and climbed up. The soles of his boots were gone and the sides were strings of raw, half-eaten leather. His legs and knees bore ugly patches of red where the slime had touched. "Well done!" called Boulton to Burl from the cabin. "Come on up before something else comes along!"