general population. You can't distinguish one of them from anyone else if he's just walking past you on the street."

Jeffries brought the car to a halt at a stop light.

"That's about the way I'd heard it," he acknowledged. "What about negative spotting? Is there a chance there might be an undiscovered latent left among our recent fellow students?"

"No chance at all," Cavender said. "The process works both ways. If they aren't, you also know it eventually—and I was sure of everyone but Greenfield over three weeks ago. She's got as tough a set of obscuring defenses as I've ever worked against. But after the jolt she got tonight, she came through clear immediately."

The light changed and the car started up. Jeffries asked, "You feel both of them can be rehabilitated?"

"Definitely," Cavender said. "Another three months of Grady's pseudoyoga might have ruined them for good. But give them around a year to settle out and they'll be all right. Then they'll get the call. It's been worth the trouble. Jones is good medium grade—and that Greenfield! She'll be a powerhouse before she's half developed. Easily the most promising prospect I've come across in six years."

"You're just as certain about Perrie Rochelle?"

"Uh-huh. Protopsi—fairly typical. She's developed as far as she ever will. It would be a complete waste of time to call her. You can't train something that just isn't there."

Jeffries grunted. "Never make a mistake, eh?"

Cavender yawned, smiled. "Never have yet, Reuben! Not in that area."

"How did you explain the sandwich to them—and Greenfield's napkin? They couldn't have bought your stage magic idea."

"No. Told them those were Dr. Al's posthypnotic suggestions. It's the other standard rationalization."

They drove on in silence for a while. Then Jeffries cleared his throat.

"Incidentally," he said. "I should apologize for the slip with the sandwich, even though it turned out to our advantage. I can't quite explain it. I was thinking of other matters at the moment, and I suppose I...."

Cavender, who had been gazing drowsily through the windshield, shook his head.

"As you say, it turned out very well, Reuben. Aside from putting the first crack in Mavis Greenfield's defenses, it shook up Dr. Al to the point where he decided to collect as much as he could tonight, cash the checks, and clear out. So he set himself up for the pinch. We probably gained as much as three or four weeks on both counts."

Jeffries nodded. "I realize that. But...."

"Well, you'd have no reason to blame yourself for the slip in any case," Cavender went on. "The fact is I'd been so confoundedly busy all afternoon and evening, I forgot to take time out for dinner. When that sandwich was being described in those mouth-watering terms, I realized I was really ravenous. At the same time I was fighting off sleep. Between the two, I went completely off guard for a moment, and it simply happened!"

He grinned. "As described, by the way, it was a terrific sandwich. That group had real imagination!" He hesitated, then put out his hand, palm up, before him. "As a matter of fact, just talking about it again seems to be putting me in a mood for seconds...."

Something shimmered for an instant in the dim air wrapped in its green tissue napkin, a second ham sandwich appeared.