Calhoun stared. His lips tightened. It was the function of the _tormal_ members of the Med Service to react to any infection more swiftly than humans could do, and to develop antibodies which destroyed that infection and could be synthesized to cure it in humans. But Murgatroyd was immune only to infections. To toxins. He was not immune to an appetite-causing molecule demanding more of itself on penalty of madness. Murgatroyd had no more inherent resistance than a man. "_Chee-chee!_" he chattered urgently. "_Chee-chee-chee!_" "It's got him," said Calhoun. He felt sickened. "It'll have me. Because I can't synthesize anything as complex as the computer says is needed to control the molecular population that makes paras!" Murgatroyd chattered again. He was indignant. He wanted something and Calhoun didn't give it to him. He could not understand so preposterous a happening. He reached up and tugged at Calhoun's trouser-leg. Calhoun picked him up and tossed him the width of the control room. He'd done it often, in play, but this was somehow different. Murgatroyd stared incredulously at Calhoun. "To break it down," said Calhoun bitterly, "I need aromatic olefines and some acetone, and acetic-acid radicals and methyl submolecular groups. To destroy it absolutely I need available unsaturated hydrocarbons--they'll be gases! And it has to be kept from reforming as it's broken up, and I may need twenty different organic radicals available at the same time! It's a month's work for a dozen competent men just to find out how to make it, and I'd have to make it in quantity for millions of people and persuade them of its necessity against all the authority of the government and the hatred of the paras, and then distribute it--" * * * * * [Illustration] Murgatroyd was upset. He wanted something that Calhoun wouldn't give him. Calhoun had shown impatience--almost an unheard-of thing! Murgatroyd squirmed unhappily. He still wanted the thing in the chest. But if he did something ingratiating.... He saw the blaster, lying on the floor. Calhoun often petted him when, imitating, he picked up something that had been dropped. Murgatroyd went over to the blaster. He looked back at Calhoun. Calhoun paced irritably up and down. The grid operator stood with clenched hands, contemplating the intolerable and the monstrous. Murgatroyd picked up the blaster. He trotted over to Calhoun. He plucked at the man's trouser-leg again. He held the blaster in the only way his tiny paw could manage it. A dark, sharp-nailed finger rested on the trigger. "_Chee-chee!_" said Murgatroyd.