Castle: I'd like to come with you. I think I can help.
Beckett: I don't think you can.
Castle: Look, I heard what you said. I did. And I think I can be a valuable asset. I play poker with the guy. I can tell when he's bluffing.
Beckett: And what about if I have to force his hand, can you be an asset then?
Castle: Look, I don't think he did it. But if he did, I want to know. That makes me objective.