There was no child left under eight years of age when the spring rains came, and the original 319 people who had come to the upper valley had dwindled to 201. In the cities the toll had been much higher.

David studied the fetal pig he was getting ready to dissect. It was wrinkled and desiccated, its bones too soft, its lymph glands lumpy, hard. Why? Why did the fourth generation decline? Harry Vlasic came to watch briefly, then walked away, his head bowed in thought. Not even he could come up with any answers, David thought, almost with satisfaction.

That night David, Walt, and Vlasic met and went over it all again. They had enough livestock to feed the two hundred people for a long time, through cloning and sexual breeding of the third generation. They could clone up to four hundred animals at a time. Chickens, swine, cattle. But if the livestock all became sterile, as seemed indicated, then the food supply was limited.

Watching the two older men, David knew that they were purposely skirting the other question. If the people also became sterile, how long would they need a continuing supply of food? He said, "We should isolate a strain of sterile mice, clone them, and test for the reemergence of fertility with each new generation of clones."

Vlasic frowned and shook his head. "If we had a dozen undergraduate students, perhaps," he said drily.

"We have to know," David said, feeling hot suddenly. "You're both acting like this is just a five-year emergency plan to tide us over a bad few years. What if it isn't that at all? Whatever is causing the sterility is present in all the animals. We have to know."

Walt looked at David briefly and said, "We don't have the time or the facilities to do any research like that."

"That's a lie," David said flatly. "We can generate all the electricity we can use, more than enough power. We have equipment we haven't even unloaded yet.…"

"Because there's no one who can use it yet," Walt said patiently.

"I can. I'll do it in my free time."

"What free time?"

"I'll find it." He stared at Walt until his uncle shrugged permission.

In June, David had his preliminary answers. "The Afour strain," he said, "has twenty-five percent potency." Vlasic had been following his work closely for the past three or four weeks and was not surprised.

Walt stared at him in disbelief. "Are you sure?" he whispered after a moment.