When a Japanese ballet dancer is mysteriously murdered, Castle and Beckett’s investigation into her secret life uncovers evidence that she was killed by a ninja, and now that ninja is coming after them.
Beckett is asked to assist with a narcotics investigation; when a routine undercover operation goes awry, Beckett is faced with dangerous men from the New York underworld.
A guilt-ridden woman confesses to a murder, but contradictory evidence and a second confession complicate the case.
The murder of a high school mean girl draws Castle back to one of his many alma maters, where he is giddy to learn that the evidence points to a surprising perpetrator--a teenage telekinetic, throwing he and Beckett into a real-life "Carrie."
When the assistant to Modern Fashion Magazine’s dictatorial editor Matilda King (guest star Frances Fisher) is found murdered, Castle and Beckett are thrust into the glitzy, ruthless world of high fashion in their search for the killer. Meanwhile Beckett's history in the modeling world gets her access to a very special wedding surprise.
When a pop star is found dead in an alley, Beckett and Castle look into her hard-partying lifestyle; a shocking revelation rocks the investigation.
The murder of a video store clerk with a secret history leads the team to Castle's father (James Brolin).
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 suspect (Joshua Gomez) in a grisly murder 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.