You understand, Mrs. Stanton," said the psychiatrist, "that a great part of Martin's trouble is mental as much 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 Because of the nature of his ailment, he has withdrawn, pulled himself away from communication with others.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'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 gradual that I never really noticed it."

Poor woman, the doctor thought. She's not well, herself. She should have married again, rather than 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 tried to do my best for Martin," Mrs. Stanton went on unhappily. "And so has Bart. 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. But when he's home, Bart helps me with Martin all the time."

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

"I don't understand," said Mrs. Stanton, breaking into sudden tears. "I don't understand 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 anything 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."