Castle takes on Detective Ethan Slaughter (Adam Baldwin) as his partner when tension between himself and Beckett rises, and he sees a new side to police work that puts him in danger.
A detective from Scotland Yard teams up with Castle and Beckett on a murder investigation.
When a bomb kills five people at a protest rally, Beckett and Castle try to solve the case by reconstructing the 47 seconds prior to the explosion.
The investigation into the death of a contestant on a popular dance competition show leads Castle and Beckett to a shocking secret that may have led to her death.
When two women are found dead dressed as fairytale characters, Castle and Beckett must race to find the killer before he strikes again!
Beckett and Castle must stop a series of events that could result in a war.
Castle and Beckett discover the killer they are pursuing is part of an international conspiracy and they must work with a CIA agent with whom Castle has a history.
Castle and Beckett must investigate a mysterious case from 1947 in order to solve the present-day murder of a treasure hunter.
The investigation into the death of a famous dog trainer leads to a reality-TV star.
When a woman is found dead in her car, the investigation leads to New York Mayor Robert Weldon (Derek Webster), one of Castle's longtime friends.
When Castle and Beckett investigate the death of a ladies' man, a twist in the case may disrupt Ryan's wedding.
Beckett and Castle wake up handcuffed together in bed in a locked room with no memory of how they got there.
The team searches for a sniper who is terrorizing New York; Beckett tries to hide her worsening PTSD from Castle and the detectives.
When a casino owner is murdered at an abandoned warehouse, suspects emerge in New York and Atlantic City; during the investigation, Castle throws an impromptu bachelor party for Ryan.
Martha and Castle are held hostage by bank robbers dressed in hospital scrubs; Beckett's rescue efforts are hindered by a strict hostage negotiator (Dean Norris).
Castle and Beckett investigate the murder of a ghost hunter who was looking into a haunting at a New York mansion.
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