Castle, Season 2

[Beckett has discovered who killed her mother, only to have to shoot him to save Castle's life]

Beckett:
It wasn't your fault, you know.

Castle:
I overstepped. I came down here to say that I'm sorry... and that I'm through. I can't shadow you any more. If it wasn't for me --

Beckett:
If it wasn't for you, I would never have found my mom's killer. And some day soon I'm gonna find the sons of bitches who had him kill her. And I'd like you around when I do. And if you tell anyone what I'm about to say there's gonna be another shooting, but... I've gotten used to you pulling my pigtails. I have a hard job, Castle, and having you around makes it a little more fun.

Castle:
...Your secret's safe with me.