Toward the end of the day Calhoun finished his task. He had a matter of six or seven cubic centimeters of clear liquid as the conclusion of a long process of culturing, and examination by microscope, and again culturing plus final filtration. He looked at a clock and calculated time. "Better wait until tomorrow," he observed, and put the bit of clear liquid in a temperature-controlled place of safekeeping. "What is it?" asked Maril. "What's it for?" "It's part of a job I have on hand," said Calhoun. He considered. "How about some music?" She looked astonished. But he set up an instrument and fed microtape into it and settled back to listen. Then there was music such as she had never heard before. It was another device to counteract isolation and monotonous between-planet voyages. To keep it from losing its effectiveness, Calhoun rationed himself on music, as on other things. Any indulgence frequently repeated would become a habit, in the sense that it would give no special pleasure when indulged in, but would make for stress if it were omitted. Calhoun deliberately went for weeks between uses of his recordings, so that music was an event to be looked forward to and cherished. When he tapered off the stirring symphonies of Kun Gee with tranquilizing, soothing melodies from the Rim School of composers, Maril regarded him with a very peculiar gaze indeed. "I think I understand now," she said slowly, "why you don't act like other people. Toward me, for example. The way you live gives you what other people have to get in crazy ways--making their work feed their vanity, and justify pride, and make them feel significant. But you can put your whole mind on your work." He thought it over. "Med Ship routine is designed to keep one healthy in his mind," he admitted. "It works pretty well. It satisfies all my mental appetites. But there are instincts...." She waited. He did not finish. "What do you do about the instincts that work and music and such things can't satisfy?" Calhoun grinned wryly, "I'm stern with them. I have to be." He stood up and plainly expected her to go into the other cabin for the night. She went. It was after breakfast time of the next ship-day when he got out the sample of clear liquid he'd worked so long to produce. "We'll see how it works," he observed. "Murgatroyd's handy in case of a slip-up. It's perfectly safe so long as he's aboard and there are only the two of us." She watched as he injected half a cc. under his own skin. Then she shivered a little. "What will it do?" "That remains to be seen." He paused a moment. "You and I," he said with some dryness, "make a perfect test for anything. If you catch something from me, it will be infectious indeed!" She gazed at him utterly without comprehension.