Humanac's flaw was that it had no way of explaining the predictions produced on its screen. It merely showed what would happen when and if certain things were done. It left it up to the human operator to figure out why things happened that way.

This was what was troubling Dr. Peccary.

He could see not the remotest relationship between his Y Hormone and the fact that a mathematical probability named Miss Terry should refuse another mathematical probability named Paul permission to climb to the top of a six-foot playground slide.

Meanwhile Staghorn had been using the fine adjustment on the geographic locator and now grunted his satisfaction. "Good! We're in the building, at least."

On the screen was a dusky corridor. On either side of it were classroom doors, some closed, some ajar. Staghorn moved his hand from the fine adjustment to the even more delicate vernier control which permitted him to shift the geographic focus inches at a time. The focus drifted slowly forward to one of the half-open doors, and then he and Dr. Peccary were able to see into the classroom.

It was deserted. Desks were thick with dust. Books, yellow with age, were strewn on the floor.

Staghorn's hand sought the vernier control again. The picture led them on down the corridor to another open door.

Again it was a scene of desolation.

"This can have nothing to do with my Y Hormone!" Peccary insisted.

"Then why is your picture on the wall there?" Staghorn said with a note of malicious pleasure.