Someone who cares. Someone who sees. Her words made a home in a hole in his chest where they seemed to fit just perfectly, and they didn't appear as if they were ready to leave. Brennan didn't really have a response to offer in turn for them, as he was already at odds to qualify her presence and her speech left him without anything to place her. It was almost becoming a fact in his mind that she was just some sort of hallucination; the last thing he would see as a sane person. Brennan tried to remember the last time he had collapsed from stress, if that time he had also hallucinated something, maybe even Kate then as well. He couldn't recall anything however, and she was questioning him now.
Who am I.
It should be a simple enough question to answer. A smart-ass would say his name; a brave man a hero; an unconfident person nobody to be concerned with. People defined themselves by what they valued, by what they do, what they say, how they treat others. Brennan defined himself by his anatomy, his genetics, his God-forsaken immunity. Slowly, over time that became everything, and what he didn't fill in, other's wrote in what they wanted. To the connected survivors of New York, Brennan was an Immune guard, previously stationed on Liberty Island, a bully to some, unpleasant to others, quiet, reserved, detached, efficient, deadly, religious, a heretic, an asshole and undeniably alone.
Even God and prayer wasn't keeping his mind intact, and despite his pleas for his own soul, it had still slipped through his fingers. Brennan remembered when he was younger, when he felt younger, when he didn't give a good goddamn about his soul, didn't think about the future. It felt like more than four years since he was able to go to sleep at night without wondering if he would wake up in the morning, since he was able to live day to day without thinking about how unbelievably isolated he has made himself. He had long ago decided to abandon his own well being to be able to take up his responsibilities without question. Once you lose everyone that kept reminding you that you were only human, it doesn't take much to convince you to let go of the last shreds. Near the end of training, he recalled a few of the people who hadn't resigned themselves to their duty called him an automaton, called him T-1000, emotionless. And that's what he was.
So what can he say to her when she asks him who he is?
"I don't know." He looked at her, right into her eyes. He may have been hyperventilating, he might not be breathing. His heart could have stopped or it was a drumbeat in his ears. "I don't know anymore."