Amy understood.

The moment she saw him standing in the hall of the apartment that wasn't hers, she understood.

He looked at her, at her surroundings, at her movements, like she looked at the rest of humanity, trying to figure out how they all fit together, what secrets they held. In her case, she was looking for the unattainable normalcy of quiet families and ordinary traumas. Perhaps he had looked for that, too, but now he was drawn to the equally fascinating ab-normalcy of gut wrenching tragedy and monstrous secrets. She knew that curiosity, too, the drive to be reassured that others were worse off, or at least as messed up as you, and that maybe they held the secrets to staving off incipient madness and constructing a life that made sense.

Living coherently, she and her brother had called it, and they had constructed their own set of secrets and rules to attain it. She had come to understand that all the walking wounded who survived and went on had their own rules, their own "coping mechanisms" as the psychologists termed it in their inadequate clinical language. She preferred rules, maybe parameters, because they implied an intentionality that mere coping mechanisms lacked. Multiple personalities were coping mechanisms, for God's sake.

She wondered what his rules were, how much he had circumscribed his own behavior and thoughts. Had he focused them inward, as she had, or outward, as the detective her brother had written about had? Both, she thought, both and then some.

She understood his frustration on realizing that the library, a collection of such randomness as to surpass any organization, was not hers. That nothing in that apartment (except the bedroom, which he knew he would not see) was hers. One's possessions give hints to one's character; one's books give hints to one's thoughts. She almost took pity on him and told him that she had read most of the books, trashy mysteries, Schopenhauer, and all.

But she didn't. He would misunderstand, and she was too aware of the precariousness of her own position to risk misunderstanding.

She had not lied when she said she always strove to be understood. She wanted understanding above all else, but it eluded her. He must be aware of the same need in himself. Why, then, did he use inscrutability as his shield?

It was so transparent. That collection of ticks and eccentricities were not all artifice, were not even mostly artifice. All the world's a stage, and he acted the part of a man who had constructed his pathologies into a weapon. And they were, but that was less intentional than he tried to make it appear.

She understood.

She could have used that understanding, struck back at him, inflicted wound for wound. Cut deeper than he had ventured to cut her. But that was one of her rules. Never give into that impulse, because the appetite for tit- for-tat never ended, and it could be so easily displaced.

Displaced aggression had to be one of the better theories modern psychology had espoused. Displaced aggression, displaced fear, displaced love, displaced curiosity. She wondered whom he was really probing when he dismantled suspects and witnesses. Wondered whose truth was too mysterious or too awful for him to puzzle out directly.

Mother, Father, Wife, or Lover. There were only so many relationships with the power to destroy oneself if the truth was too well known.

She understood.

Amy knew that her last words would injure him, but they were also the only convincing forgiveness she could offer. And that purpose was sufficient justification. One should never use the truth just to injure, but sometimes injury was the necessary byproduct and sometimes it was the very instrumentality by which the ultimate benefits would be achieved.

He was transparent, and she could have gone farther, could have torn him down as he attempted to do to her. Men were always more vulnerable to that destruction, with their flimsy pretensions to invulnerability.

That was another rule. Always be vulnerable, let yourself hurt. It's when you don't hurt, when you become numb, that the cold of malice and cruelty has crept in and you become what created the need for all these rules in the first place.

Amy knew that he would understand all of this, perhaps already did - he was older, after all - in a way that only her brother had approached. She wondered if he ever let an interrogation become a conversation, with its noncompetitive give and take. Wondered if he would make an exception for her.

She wondered if he'd learned that inflexible rules were as sure a road to madness as no rules at all. Probably. He could never have survived this long if he hadn't.

She understood, without benefit of any details or police files. And when she saw him in the restaurant, sitting at her old table, waiting for a stranger to come and finally reveal to him the puzzle pieces he was missing, she knew he understood, too.