A guard moved abruptly overhead. The motion caught MacVickers' eye. Something screamed sharply in his head: Pendleton's voice saying, "They breathe through the skin. All their sense organs...." He sensed rather than saw Birek's fist coming. He twisted, enough to take the worst of it on his shoulder. It knocked him halfway across the deck. And then the current came on. It was weak, but it made him jerk and twitch. He scrambled up on the pitching deck and started to speak. Birek was coming again, leisurely, smiling. Then, quite suddenly, the hatch cover clanged open, signalling the change of the shifts. MacVickers stood still for a second. Then he laughed, a queer little chuckle, and made a rush for the hatch. III He went down it with Birek's hand brushing past his head. Men yelled and cursed. He trampled on them ruthlessly. The ones lower down fell off the ladder to avoid his feet. There was a clamor up above. Hands grabbed at him. He lashed out, kicking and butting. His rush carried him through and out across the pit, toward the space between the end points of the horseshoe circuit. He slowed down, then. The guards had noticed the scuffle. But it seemed to be only the shift changing, and MacVickers looked like a man going peacefully for oil. Peacefully. The blood thundered in his head, he was cold, and the skin of his back crawled. Men shoved and swore back by the ladder. He went on, not too fast, fighting the electric shiver in his brain. Fuel and lubricating oils were brought up, presumably from tanks in a still lower level, by big pressure pumps. All three sets of pumps, intake, outlet, and oil, worked off the same compressed-air unit. He set the lubricating-oil pump going and rattled cans into place. The men of his shift were straggling out from the ladder, twitching from the light current, scared, angry, but uncertain. There was a subtle change in the attitude of the Europan guards. Their movements were sluggish, faintly uncertain. MacVickers grinned viciously. Seasick. They'd be sicker--if they didn't get him too soon. The surging pitch of the bell was getting worse. The tide was rising, and the mud was playing with the bell like a child throwing a ball. Nausea began to clutch at MacVickers' stomach. The pressure-gage on the pump was rising. He let it rise, praying, his grey-green eyes hot and bright. Going with the motion of the deck, he sprawled over against the intake pumps. He spun the wheel on the pressure-control as far as it would go. A light wrench, chained so that it could not be thrown, lay at his feet. He picked it up, his hand jerking and tingling, and began to work at the air-pipe coupling. Hands gripped his shoulder suddenly, slewing him around. The yellow eyes of Janu the Martian glared into his. "What are you doing here, Earthman? This is my station."