Castle 4x22 "Undead Again" Sneak Peek (5) CASTLE - "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 -- on "Castle," MONDAY, APRIL 30 (10:01-11:00 p.m., ET), on the ABC Television Network. (ABC/RICHARD CARTWRIGHT) NATHAN FILLION, STANA KATIC