The murder of a man connected to smuggling Turkish relics sends Castle, Beckett and the 12th Precinct on a search for a stolen antique believed to be Aladdin's lamp, in hopes that it can lead them to the killer.
A clue at the scene of the death of an armored-car driver leads Beckett and Castle back to an old case solved by Esposito. But complications arise when they learn that Esposito might not have been telling them everything about his past with the culprit.
When a recruit officer at the NYPD Academy is killed, Beckett and the team go back to their old training ground to investigate. Meanwhile, Castle must reckon with a decision with profound consequences for him and Beckett.
Castle returns to the City of Angels in search of answers about his missing time. But things take a deadly turn when he's recruited by the legendary Greatest Detective Society to help solve a murder.
Beckett and the 12th Precinct look into the murder of an English as a Second Langue student. But when the victim's class won't talk to the police, Castle goes undercover as a French Canadian immigrant and learns that the victim was more than he seemed.
Castle is captured and forced to work with strangers to solve deranged puzzles and mind games, while Beckett and the 12th Precinct must race against time to rescue Castle and catch a killer.
When the son of a Russian diplomat turns up murdered, Beckett and Castle find themselves in a dangerous game of international crime and punishment, with Castle having to entertain a jovial Russian security officer who winds up more involved than anyone planned.
Castle finally gets his day in court when he takes the stand as the key witness to a murder from five months ago. But when new information suddenly arises, he and Beckett must race against the clock to prevent a miscarriage of justice
When a body is found in the theater of Martha's latest show, Castle and Beckett's investigation leads them into the unexpectedly dangerous world of competitive a capella.
Castle and Beckett investigate the murder of a cruise ship entertainer, only to find themselves trapped at sea with the killer.