After a bike messenger, carrying a package with content that is able to free a wrongly convicted man from prison, is brutally murdered, Castle and Beckett need to investigate the case. But they are surprised to find out that the tragic death is linked to another murder case previously investigated by Captain Montgomery. Now, in order to solve the new murder, Castle and Beckett must dig deep and discover all the secrets of a prominent New York family.

Mysteries abound when a family returns from vacation to discover a dead man in their daughter's bed. Thinking they're investigating the murder of a squatter, Castle and Beckett soon find themselves unraveling a multi-million dollar heist. Meanwhile, Castle tries to keep Beckett from finding out that they've been romantically linked when he's featured as one of New York's 10 most eligible bachelors.

An unknown woman falls out of a casket along with the original deceased when pallbearers lose control of the casket at a funeral; the investigation takes Beckett and Castle into the world of amorous, bed-hopping physicians.

During the high profile trial of a murdered socialite, a juror tumbles out of the jury box....dead.

A crew of bank robbers disguised as classic television doctors take hostages which include Castle and Martha. But things are complicated by the fact that Beckett's on the outside having her every move scrutinized by a hostage negotiator and Castle's on the inside with information that the hostages are just a distraction for a more ominous plan.

When Castle and Beckett investigate the killing of a treasure hunter, they discover the case is linked to a mysterious homicide from 1947 involving a hard-boiled private detective. Castle realizes the only way to solve the present-day murder is to solve the murder from the past. The 1947 case comes to life through stylized flashbacks, featuring Castle as the private eye and Beckett as a femme fatale.

A repossessed storage unit, treasure seekers and Manhattan socialites all come together in the case of a woman inexplicably murdered. Castle decides to enter the storage unit auction to see if anything inside might have led to her killing.

When a powerful divorce attorney who only represented women is murdered, Castle and Beckett are confronted with a plethora of angry ex-husbands, any one of whom could be the murderer. Meanwhile, Castle's ex-wife (Darby Stanchfield), Meredith, moves into the loft to take care of Alexis while she recovers from Mono, and to make matters worse, Beckett is also forced to move in while her apartment is being fumigated, causing tension, humor and more than a little awkwardness

When a man is found dead in an industrial cake mixer, Castle and Beckett trace the murder to an Irish gang in Staten Island and a beautiful bar owner named Siobhan O’Doul. Much to everyone’s surprise, Detective Ryan has a complicated history with Siobhan and the Staten Island crime family from his days working undercover in narcotics. When the case hits a dead end, Ryan must go back undercover to expose the killer, complicating his relationship with his wife.

A desperate young murder suspect, Emma Briggs, takes hostages at gunpoint then mysteriously insists that she will only negotiate with one person: Richard Castle.

The murder of a young video store clerk takes a strange turn when the team discovers his past history as a high-level hacker. But it's nothing compared to the shock Castle receives when their investigation leads them straight to his father, Jackson Hunt.

A secret investigation conducted by Beckett related to her mother's murder goes awry when a man she has been surveilling is killed. When evidence links Beckett to the victim, she and Castle become the targets of a manhunt that puts both of them in grave danger.

Castle takes on a routine P.I. case, but the investigation turns deadly when he witnesses a murder.

When Sid Ross, the powerful creator of a long-running sketch comedy show is killed, Castle and Beckett are called to investigate. But as they delve into the victim’s life and the colorful world of “Saturday Night Tonight,” they uncover a shocking secret that may explain Sid’s murder.

After passing the Captain's exam last season, Beckett was surprised with an offer to run for State Senate. In the action packed season premiere, Castle and Beckett are adjusting to Beckett's career change, when a call from a mysterious stranger sets off an explosive chain of events. There are two sides to every story, and this unique two-parter will explore the same story from each of their perspectives, first from Castle's side as he searches for Beckett.

Beckett's side of her abrupt disappearance is revealed. After receiving a mysterious tip from her past, Beckett is launched into a fight for her life, with a team of mercenaries hot on her trail. While Castle investigates why his wife is on the run, Beckett must figure out who wants her dead, before they can finish the job.

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.

With their best lead in hand, Castle and Beckett are ready to take on LokSat. But an unforeseen twist puts their case – and their lives – in jeopardy.