"Just so. Its enzyme system is its vulnerability. Enzyme systems operate under specific optimum conditions, right? And every known enzyme system can be inactivated by adverse conditions of one sort or another. A physical approach may tell us how in this case. Meanwhile we will be on emergency rations, and hope that we don't starve to death finding out." The Black Doctor paused, looking at the men around him. "And in case you are thinking of enlisting help from outside, forget it. I've sent plague-warnings out for Galactic relay. We have this thing isolated, and we're going to keep it that way as long as I command this ship." They went gloomily back to their laboratories to plan their frontal attack. That was the night that Hrunta disappeared. * * * * * He was gone when they came to wake him from his sleep period. His bunk had been slept in, but he wasn't in it. In fact, he wasn't anywhere on the ship. "But he couldn't just vanish!" the Black Doctor burst out when they told him the news. "Maybe he's hiding somewhere. Maybe this business was working on his mind." Green Doctor Stone took a crew of men to search the ship again, even though he considered it a waste of precious time. He had his private convictions about where Hrunta had gone. So did every other man on the ship, including Jenkins. The _hlorg_ had stopped eating. Huge and round and wet and ugly, it squatted in the after-hold, quivering gently, without any other sign of life. Surfeited. Like a fat man after a turkey dinner. Jenkins reviewed progress with the others. No stone had been left unturned. They had sliced the _hlorg_, and squeezed it. They had boiled it and frozen it. They had dropped chunks of it in acid vats and covered other chunks with desiccants and alkalis. Nothing seemed to bother it. A cold environment slowed down its activity, true, but it also stimulated the process of fission. Warmed up again, the portions sucked back together again and resumed eating. Heat was a little more effective, but not much. It stunned the creature for a brief period, but it would not burn. It hissed frightfully and gave off an overpowering stench, and curled up at the edges, but as soon as the heat was turned off it began to recover. In Hrunta's lab chunks of the _hlorg_ sat in a dozen vats on tables and in sinks. Some contained antibiotics, some concentrated acids, some desiccants. In each vat a blob of pink protoplasm wiggled happily, showing no sign of discomfiture. On another table were the remains of Hrunta's (unsuccessful) attempt to prepare an anti-_hlorg_ serum. But no Hrunta. "He was down there with the thing all day," Bowman said sadly. "He felt it was his responsibility, really. Hrunta thought biochemistry was the answer to all things, of course. Very conscientious man." "But he was in _bed_." "He claimed he did his best thinking in bed. Maybe he had a brainstorm and went down to try it out, and--"