things to tell me.

I beat him to it. "Take that injured glower off your puss," I snapped.
"Your business is testing people for their Psi powers. Why shouldn't I
call on you for help? What are friends for?"

"For a friend I might," Lindstrom said. "You don't rate that well with
me any more."

"I'll try to bear up under it," I told him. "In the meantime, this is
Mary Hall, a reputed Psi. Her power is HC."

He was interested in spite of himself. "Hallucination?" he said. "We
don't see much of that, Miss Hall. And you claim you can demonstrate
this power under controlled conditions?" These eggheads all talk
alike.

Mary shook her head. "No, I certainly do not. I'm as Normal as you
are, Professor." He sagged slightly in disappointment.

"Well," Lindstrom said. "This is going to be difficult to prove, Miss
Hall. Merely by withholding your HC ability, you can act Normal--but
what would that prove?"

She turned to me. "I thought you said you had a way to get me off the
hook," she protested. "How are we--?"

"Quiet," I told her. "I didn't come up here for a lecture in logic.
Especially from a dumb blonde." She started to bristle, but thought
better of it.

"It goes like this, Prof," I said. "This innocent looking piece of
fluff was caught slipping a five-dollar bill to a teller at a bank
down town, and asking for change for a hundred dollar bill. She says
it was nothing more than sleight of hand. You are an experienced
observer. I want you to watch her work her little trick. If she can
fool us, and not use Psi, the legal position is that she didn't need
Psi to fool the teller." I turned to her. "And the logical principle,
Miss Aristotle," I told her, "is equally simple: Occam's Razor. Prefer
the simpler explanation. Can you show us how you palmed the hundred
and slipped the teller a five?"

"You'll be watching for it," Mary protested, letting those ripe lips
pout.

"I suppose the teller wasn't? It's his business to watch the bills
when he's making change." I took out my wallet and handed her a one
and a five. "Hand me the one and make me think it's the five," I said.

Lindstrom leaned his elbows on the black composition top of the lab
bench, watching her narrowly. Mary got down off her stool and came
over closer to me, smoothing the two bills in her fingers. The five
was on top.

"I'd like change for a five," she said, handing it to me. She worked
it three times while we watched.

"Utterly smooth," Lindstro