When a rising young pop star is found dead in an alley, Castle and Beckett delve into the victim's out-of-control hard-partying lifestyle, but as they dig deeper, a shocking revelation threatens to rock their investigation.
The murder of a PA at a top fashion magazine brings Castle and Beckett face to face with a tangled web of suspicion and corporate politics - and with the magazine's formidable editor, who still remembers Beckett's brief career as a model.
Castle and Beckett are baffled when a confused woman with an unshakable alibi gives a detailed and convincing confession to a murder. Then a second person walks into the precinct and makes the same confession. And then a third.
Beckett is recruited to assist on a Narcotics investigation, but a routine mission turns deadly when an undercover operation goes awry. To survive, Beckett must engage in a battle against some of the most dangerous men in the New York underworld - including a powerful enemy from her past.
Investigating the killing of a Japanese ballerina, Castle and Beckett find a shrine with the murder weapon in an old factory. Then, when the two are separated, Castle is ambushed by a hooded attacker bearing all the hallmarks of a ninja.
When construction workers uncover a mobster's body buried in concrete for 35 years, Castle and Beckett must try to talk to a fellow mafioso so stricken with grief that he lives as a recluse in a Seventies time-warp.
A man Beckett has been secretly following is found dead - and then a notorious criminal involved in the first death is killed with Beckett's own gun. Faced with an elaborate frame-up, she has no choice but to run.
The wait is finally over for Castle as the wedding day approaches. Kate discovers that she's still married to her college sweetheart, and visits him to get a divorce. But he has problems of his own, bigger than anyone could imagine.
When a pool shark is murdered by an unseen force, Castle and Beckett uncover evidence that the killer may have paranormal powers. Meanwhile, Castle and Beckett attempt to get their lives back to normal following his disappearance.
Beckett and Castle investigate the shooting of an ice cream vendor and clues lead them to suspect that an unknown second grade child might be able to help them solve the case; Castle goes undercover at a school to try and find the student.
When a web celebrity is murdered, Castle and Beckett explore the flashy world of internet fame, but when the killer posts pictures from the crime scene on a photo-sharing site, they realise they are up against a social media sociopath who may strike again.
After Castle finds out that his most beloved 1980's movie star has been murdered, he and Beckett receive aid from a group of older action heroes, and investigate the man's heavily guarded past in hopes that it will lead them to his killer.