Bones, Season 1

Brennan:
Why are you nice to me?

Booth:
Because. Because they think they get away with it.

Brennan:
What?

Booth:
They burn their victim, they blow him up, they toss him in the ocean, they bury him in the desert, they throw 'em to wood chippers. Sometimes, you know, years go by. They relax. Then they start living their lives like they didn't do anything wrong. Like they didn't spend somebody else's life in order to get what they got. They think they're safe from retribution. You make those bastards unsafe. That's why I'm nice to you.

Brennan:
I couldn't do that without you, Booth.

Booth:
Yeah. So, um, you should be a little nicer to me, huh?

Brennan:
I really should.