Castle: Look, maybe Damian is a cheater and a bum and a bad husband.
Castle: But that doesn't make him a killer. And you keep looking at me like I'm crazy for believing in him, but that's just because you don't know him.
Beckett: Castle, neither do you. The Damian that you think you know doesn't exist. You made him up, just like you made up Derrick Storm, just like you made up Nikki Heat. He's a character in a story that you told yourself when you were a homesick 14-year-old little boy. Maybe it's time to let him go.