A cool new kid arrives in the building, causing Booker and Levi to fight Nia and Tess for his attention.

When an ex-con is mysteriously slain in an alley, Castle and Beckett believe a vigilante is behind the murder. But efforts to identify their suspect are thwarted when they discover…

Detective Beckett fights for her life as Castle, plagued by guilt over his role in the events, struggles to uncover who’s behind her brutal shooting. Meanwhile, back at the precinct,…

Picking up the morning after, Castle and Beckett now have to decide if they’re a couple or was it just a onetime deal. But before they can tackle that, they…

Charlie sees a therapist to learn how to deal with Alan’s emotional insecurities.

Penny squares off with a new beautiful female neighbor who may become the building’s “new Penny.”

Marshall tries to get used to being single in a world that is very coupled-oriented. Barney intended one-night-stand won’t go away. Barney uses Lily to get out of his “horrifying”…