nderstand why Martin should behave this way! Why should he just sit
there with his eyes closed and ignore us both?"

The doctor comforted her in a warmly professional manner, then, as her
tears subsided, he said: "We don't understand all of the factors
ourselves, Mrs. Stanton. Martin's reactions are, I admit, unusual. His
behavior doesn't quite follow the pattern that we usually expect from such
cases as this. His physical disability has drastically modified the course
of his mental development, and, at the same time, makes it difficult for
us to make any analysis of is mental state."

"Is there _any_thing you can do, Doctor?"

"We don't know yet," he said gently. He considered for a moment, then
said: "Mrs. Stanton, I'd like for you to leave both the boys here for a
few days, so that we can perform further tests. That will help us a great
deal in getting at the root of Martin's trouble."

She looked at him with a little surprise. "Why, yes, of course. But ...
why should Bart stay?"

The doctor weighed his words carefully before he spoke.

"Bart is our control, Mrs. Stanton. Since the boys are genetically
identical, they should have been a great deal alike in personality if it
hadn't been for Martin's accident. In other words, our tests of Bart will
tell us what Martin _should_ be like. That way we can tell just how much
and in what way Martin deviates from what he should ideally be. Do you
understand?"

"Yes. Yes, I see. All right, Doctor--whatever you say."

After Mrs. Stanton had left, the psychiatrist sat quietly in his chair and
stared thoughtfully at his desk top for several minutes. Then, making his
decision, he picked up a small book that lay on his desk and looked up a
number in Arlington, Virginia. He punched out the number on his phone, and
when the face appeared on his screen, he said: "Hello, Sidney. Look, I
have a very interesting case out here that I'd like to talk to you about.
Do you happen to have a telepath who's strong enough to take a meshing
with an insane mind? If my suspicions are correct, I'll need a man with an
impregnable sense of identity, because he's going to get into the weirdest
situation I've ever come across."

XIII

_Pok! Pok! Ping!_

_Pok! Pok! Ping!_

_Pok! Pok! Ping!_

The action in the handball court was beautiful to watch. The robot
mechanism behind Bart Stanton would fire out a ball at random intervals
ranging from a tenth to a quarter of a second, bouncing them