Martian plants produced different isomers from those on Earth. Since the synthetic foods turned out to be Mars-normal, that was probably the more natural form. Research designed to let the early colonists live off native food here had turned up an enzyme that enabled the body to handle either isomer. In a few weeks of eating Martian or synthetic food, the body adapted; without more enzyme, it lost its power to handle Earth-normal food. The cheapness of synthetics and the discovery that many diseases common to Earth would not attack Mars-normal bodies led to the wide use of synthetics on Earth. No pariah could have been expected to afford Earth-normal. Feldman finished the soup, and found a cigarette that was smokable. "Any objections if I sit in the waiting room?" He'd expected a rejection, but the counterman only shrugged. The waiting room was almost dark and the air was chilly, but there was normal pressure. He found a bench and slumped onto it, lighting his cigarette. He'd miss the smokes--but probably not for long. He finished the cigarette reluctantly and sat huddled on the bench, waiting for morning. The airlock opened later, and feet sounded on the boards of the waiting-room floor, but he didn't look up until a thin beam of light hit him. Then he sighed and nodded. The shoes, made of some odd fiber, didn't look like those of a cop, but this was Mars. He could see only a hulking shadow behind the light. "You the man who was a medical doctor?" The voice was dry and old. "Yeah," Feldman answered. "Once." "Good. Thought that space crewman was just lying drunk at first. Come along, Doc." "Why?" It didn't matter, but if they wanted him to move on, they'd have to push a little harder. The light swung up to show the other. He was the shade of old leather with a bleached patch of sandy hair and the deepest gray eyes Feldman had ever seen. It was a face that could have belonged to a country storekeeper in New England, with the same hint of dry humor. The man was dressed in padded levis and a leather jacket of unguessable age. His aspirator seemed worn and patched, and one big hand fumbled with it. "Because we're friends, Doc," the voice drawled at him. "Because you might as well come with us as sit here. Maybe we have a job for you." Feldman shrugged and stood up. If the man was a Lobby policeman, he was different from the usual kind. Nothing could be worse than the present prospects. They went out through the doors of the waiting room toward a rattletrap vehicle. It looked something like a cross between a schoolboy's jalopy and a scaled-down army tank of former times. The treads were caterpillar style, and the stubby body was completely enclosed. A tiny airlock stuck out from the rear. Two men were inside, both bearded. The old man grinned at them. "Mark, Lou, meet Doc Feldman. Sit, Doc. I'm Jake Mullens, and you might say we were farmers."