A hatch clanged open, and there were more footsteps down the main corridor as a change of guards hurried by. There was a rumble of voices, and Tom listened to catch the words. "... don't care what you think, the boss says tighten it up...." "But they got them locked in...." "So tell it to the boss. We're supposed to check every compartment in the section every hour. Now get moving...." The footsteps moved up and down the corridor then, and Tom heard hatches clanging open. If they sent a light down this spur ... he turned to the hatch, spun the big wheel on the door, and slipped inside just as the footsteps came closer. The stench inside was almost overpowering. The big, darkened room was extremely warm, the air damp with vapor. The plastic-coated walls streamed with moisture. Against the walls Tom could see the great hydroponic vats that held the yeast and algae cultures that fed the crew of the ship. Water was splashing in one of the vats, and there was a gurgling sound as nutrient broth drained out, to be replaced with fresh. He moved swiftly across the compartment, into a darkened area behind the rows of vats, and crouched down. He heard footsteps, and the ring of metal as the hatchway came open. One of the guards walked in, peered into the gloom, wrinkled his nose, and walked out again, closing the hatchway behind him. It would do for a while ... if he didn't suffocate ... but if this ship was organized like smaller ones, it would be a blind alley. Modern hydroponic tanks did not require much servicing, once the cultures were growing; the broth was drained automatically and sluiced through a series of pipes to the rendering plant where the yeasts could be flavored and pressed into surrogate steaks and other items for spaceship cuisine. There would be no other entrances, no way to leave except the way he had come in. And with the guards on duty, that was out of the question. He waited, listening, as the check-down continued in nearby compartments. Then silence fell again. The heavy yeast aroma had grown more and more oppressive; now suddenly a fan went on with a whir, and a cool draft of freshened reprocessed air poured down from the ventilator shaft above his head. Getting into the orbit-ship had been easier than he had hoped. In the excitement as the new prisoners were brought aboard, security measures had been lax. No one had expected a third visitor; in consequence, no one looked for one. Huge as it was, the Jupiter Equilateral ship had never been planned as a prison, and it had taken time to stake out the guards in a security system that was at all effective. In addition, every man who served as a guard had been taken from duty somewhere else on the ship.