If there were harmful bacteria aboard the ship, they should have struck many days ago. There was no disease in space itself. Gas? If such ships as the _By Jove!_ carried any sort of gas, Albrekt didn't know about it. He had been briefed on the weapons he might face. Surely gas would have been mentioned. Perhaps it was chance, or perhaps some part of his mind was swiftly scanning what he had learned through his reading of the last few days: his eyes fell on a bank of dials ranged side by side on the control board. The hands of all of them were lined up at the same angle--all but one. It had sunk far to the left. The legend above the bank of dials read: "OXYGEN." The plate below the lagging dial read: "Control Room." Albrekt unstrapped himself from the chair with nervously fumbling hands. Somehow the crew of the _By Jove!_ was interfering with his oxygen supply. Albrekt was beginning to feel a little nauseated. His head throbbed. He pushed himself across the control room and grabbed the helmet of the spacesuit that hung there. He did not take time to put on the suit itself, but pulled the helmet down over his head and switched on the suit's oxygen supply. In a moment his head cleared, leaving only a slight headache. As well as Albrekt remembered from the reading tapes, the ship's oxygen supply was on one of the lowest decks. The crew evidently had blocked the line to the control room. "You'd think there'd be some alarm system for that sort of thing," he muttered to himself. But then, of course, the hull had not been punctured. The dials were supposed to be checked frequently. The question that faced Albrekt now was how to get out of this trap. He couldn't live in the spacesuit indefinitely. His hand brushed the heat gun at his side. Filling his lungs with deep gulps, he ducked from beneath the helmet and returned to the control board. He unlocked and opened the hatch to the navigation deck below. There was an upward swirl of air, and Albrekt permitted himself to breathe again. A head poked itself cautiously up the companionway. Carrel. The captain's face was a strong one, lined with years of decision, golden-brown with the tan that one gets only from years in the thin air of Mars. Carrel's dark hair was beginning to gray, but his electric blue eyes were still young. He stopped when he saw Albrekt at the control board. Albrekt held the heat gun on the captain steadily. "I'm not anywhere near overcome," said Albrekt. "You'd better turn around and go back down." Carrel did. As long as the hatch stayed open, oxygen could not be cut off from the control room. Albrekt decided he could afford to leave it open, since he had possession of the weapons. He would have to lock it while asleep, of course. But, even with the oxygen supply cut off, the control room should contain enough to carry him for eight hours. If not, he could set an alarm to wake him every four hours, or even every two hours, to open the hatch and refresh his air.