Summary:In the first episode of a two-part “Castle” event, Castle and Beckett pursue a ruthless killer who, they discover, is part of a sinister, international conspiracy. Castle and Beckett are joined on the case by Sophia Conrad (guest star Jennifer Beals), a smart, sexy CIA operative who has a complicated past with Castle. Josh Stamberg also guest stars as Martin Danberg, an intelligence officer

Summary:In the explosive conclusion of a two-part story arc that began last week with "Pandora," Castle & Beckett race to find the "Linchpin" in order to stop the first domino in a chain of events which will plunge the United States into war.

Summary:When a woman dressed as Red Riding Hood is found dead in the woods with claw marks covering her body, and soon after a murdered Snow White is discovered with a poison apple in her hand, Castle & Beckett find themselves on a Grimm hunt to catch a fairytale killer before he kills again. But nothing is as it seems in a case filled with deceit, betrayal, secrets and murder.

Summary:When Odette Morton, a contestant on the hit competition show "A Night of Dance", is found murdered in her dressing room, Castle and Beckett must navigate the case's many twists and twirls without stepping on each other's toes. But as they delve into Odette's past, they discover that this reality starlet was harboring a shocking secret that may have led to her death.

Summary:When a bomb explodes at a protest rally killing five people, Castle & Beckett realize the key to solving the case is to reconstruct the 47 seconds prior to the explosion. Using video and witness accounts, they uncover the shocking truth about who planted the bomb.

Summary:A devilishly handsome detective from Scotland Yard, Simon Hunt, teams up with Castle & Beckett to find the person responsible for the murder of his friend’s daughter. Also, Charles Shaughnessy plays Nigel Winthrop, the Deputy General at the British Consulate whom Castle & Beckett suspect is up to more than just ambassadorial balls and diplomatic luncheons. Meanwhile, Lanie convinces Beckett that she needs to make a move on Castle before it is too late.

Summary: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.

Summary: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.

Summary: In the fourth season finale, Castle and Beckett confront the issues between them while they must deal with a case that takes them back to Beckett’s shooting and her mother’s murder.