Castle and Beckett Rush to the Scene in Castle Season 4, Episode 22: "Undead Again"
When Castle and Beckett investigate the murder of a man with human bite marks on his body, Castle's wild theories start flying. But none are as wild as what their only witness insists happened — a Zombie attack. As the evidence pointing towards an undead assailant piles up, the team plunges into New York's Zombie subculture to find the killer and bring him in — dead, undead or alive.
Original Air Date: Castle Season 4, Episode 22: "Undead Again" airs on Monday, April 30, 2012 at 10 p.m. ET on ABC.