"You understand, Mrs. Stanton," said the psychiatrist, "that a great part of Martin's trouble is mental as well as physical. Because of the nature of his ailment, he has withdrawn, pulled himself away from communication with others. If these symptoms had been brought to my attention earlier, the mental disturbance might have been more easily analyzed and treated."

"I suppose so. I'm sorry, Doctor," said Mrs. Stanton. Her manner betrayed weariness and pain. "It was so ... so difficult. Martin could never talk very well, you know, and he just talked less and less as the years went by. It was so slow and so gradual that I never really noticed it."

Poor woman, the doctor thought. She's not well, herself. She should have married again, years ago, rather than force herself to carry the whole burden alone. Her role as a doting mother hasn't helped either of the boys to overcome the handicaps that were already present.

"I've honestly tried to do my very best with Martin," Mrs. Stanton went on unhappily. "And so has Bart, I know. When they were younger, Bart used to take him out all the time. They went everywhere together. Of course, I don't expect Bart to do that so much any more. He has his own life to live. He can't take Martin out on dates or things like that. He has interests outside the home now, like other boys his age. That's only normal. But when he's at home, Bart helps me with Martin all the time."

"I understand," said the psychiatrist. This is no time to tell her that Bartholomew's tests indicate that he has subconsciously resented Martin's presence for a long time, he thought. She has enough to worry about.

"I don't understand," said Mrs. Stanton, breaking into sudden tears. "I just don't understand why Martin should behave this way! Why should he just sit there with his eyes closed and ignore everybody? Why should he ignore his mother and his brother? Why?"

The doctor comforted her in a warmly professional manner, then, as her tears subsided, he said, "We don't understand all the factors ourselves, Mrs. Stanton. At first glance, Martin's reactions appear to be those one would expect of schizophrenic withdrawal. But there are certain aspects of the case that make it unusual. His behavior doesn't quite follow the pattern we usually expect from such cases as this. His extreme physical disability has drastically modified the course of his mental development, and, at the same time, made it difficult for us to make any analysis of his mental state." If only, he added to himself, she had followed the advice of her family physician, years ago. If she had only put the boy under the proper care, none of this would have happened.

"Is there anything we can do, Doctor?" she asked.

"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 of the boys here for a few days, so that we can perform further tests. That will help us a great deal in evaluating the circumstances, and help us get at the root of Martin's trouble."

She looked at him with a little surprise. "Why, yes, of course—if you think it's necessary. But ... why should Bart stay?"

The doctor weighed his words carefully before he spoke.

"Bart will be what we call a 'control', Mrs. Stanton. Since the boys are genetically identical, they should have been a great deal alike, in personality as well as in body, 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. Busy right now?"

"Not particularly. Not for a few minutes. What's up?"

"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 will need a man with an absolutely impregnable sense of identity, because he's going to get into the weirdest situation I've ever come across."