Based on "Who You'd Be Today" by Kenny Chesney.
Disclaimer: I don't own any CSI NY characters, and my parts about Stella and Flack are strictly fictional, just my perspective I guess.
Mac was sitting at his desk staring at a small picture in his hand. He hated this day. It came every year and brought the same pain. He had Peyton now, but it was still hard for him to think about Claire. Especially on this day-their anniversary. He started to wonder about what it would've been like if she would've survived. Would they have had kids? He had wanted to, and so had she but they never got around to it. He pictured her in his head. Her beautiful smile and her laugh. He began to remember the last thing he had said to her that day.
"I got a call. I'll see you when I get home," he had said to her, standing in the doorway of the bedroom. She was getting herself ready for work. He had walked over to her kissed her and left the apartment. He could remember now he hadn't even said he loved her.
He remembered the call he had gotten after the towers had fallen. He found out that Claire had been inside, and that most likely she wasn't going to make it out alive. It had been six years now and she hadn't been found- not a trace of her.