Castle and Beckett suspect a serial arsonist of murder; Jenny goes into labor.
A dying man leaves a baby with a priest; Castle and Beckett end up taking care of the baby while they investigate.
When a woman who looks very similar to Lanie is murdered, the team thinks the killer may be targeting members of the 12th precinct.
When a well-known relationship therapist is murdered, it seems that she was targeted due to the secrets she knew about her powerful and elite clients.
Alexis asks Castle for help proving a death row inmate's innocence 72 hours before his execution, but they uncover a secret that could seal the man's fate.
As Castle and Beckett investigate the ritualistic murder of a young woman, they find strange symbols in the victim's apartment; Castle struggles with Alexis' decision to move in with Pi.
A murder suspect claims he has traveled back in time to prevent terrible events from unfolding.
A desperate murder suspect with a hostage insists on negotiating with Castle.
Agents Beckett and McCord arrive to take over Castle and the guys' investigation into the death of a former child star, creating tension in the precinct.
Beckett races to find a stolen toxin capable of killing thousands of people; Castle has less than 24 hours to live after being exposed to the chemical weapon.
Beckett and Castle face the consequences of their decisions during a high-stakes investigation.
Season six begins where season five left off. Will Beckett accept Castle's proposal?
An interview with a federal law enforcement agency forces Beckett to reconsider her career and her relationship with Castle; a young woman's body is found inside a flop house's water tank.
When a government whistleblower is murdered, Beckett and Castle must figure out who is responsible and determine why Homeland Security is trying to take over the case.
When Beckett steps on a pressure-sensitive bomb, the team searches for a way to save her while Castle distracts her by talking about their relationship.
When Beckett is tasked with protecting a charming billionaire whose life is in danger, she reflects on her relationship with Castle; consumed with jealousy, Castle tries to solve the case as quickly as possible.
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