Why do you know this?

On the subject of serial killers:

Curtis: What are you watching?

TV show: " . . . Green River . . ."

Curtis: Oh, is this about the Green River Killer?

Sally: Yeah.

Curtis: Who is he, again? Was he the church guy?

Sally: I don't know. I honestly don't know much about him.

Curtis: So, not the guy who went to church a lot?

Sally: He might have. But are you thinking of Dennis Rader?

Curtis: Maybe?

Sally: BTK?

Curtis: Yeah, I am. You're right.

Sally: It's easy to get them confused. They were arrested at practically the same time, and they had similar MOs. Wait, I think I know the Green River Killer's name. Gary . . . Gary . . . Gary! Gary Leon Ridgway. That was it. But I don't know a whole lot more about him.

Curtis: You know more than I'm comfortable knowing that you know. Why do you know this stuff?

Sally: People ask me that every time we talk about serial killers.

Curtis: I'm guessing this happens a lot.