Castle (2009): Season 4, Episode 21 - ProjectFreeTV

4 - 21: Headhunters

With tensions rising between Castle and Beckett, Castle finds himself a new partner -- Detective Ethan Slaughter, a tough and colorful cop from the city's gang unit. But Castle gets more than he bargained for when Slaughter shows him a grittier side of police work that puts Castle in the line of fire like never before.