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.

When the body of a local college fraternity student is found gruesomely murdered, Castle has to go undercover as a professor in order to gain access to the victim's world. However, he and Beckett soon discover that behind the fun and games of college are some darker secrets the university wants to keep hidden.

When Castle's idol, a famously reclusive author, turns up dead, Castle is determined to solve his hero's murder. But as he and Beckett dig deeper, they discover that truth is stranger than fiction.

Detective Slaughter returns to enlist Castle’s help in solving a high-stakes robbery case. But when a body is found linked to the crime, Slaughter becomes the number one suspect in the heist turned murder, while Castle has to determine whether he’s guilty or help to prove he’s innocent.

In order to hunt down the brutal murderer of a grifting seducer, Castle & Beckett must investigate New York’s elite. Meanwhile, Castle plans to surprise Beckett on their one-year wedding anniversary.

Castle and Beckett investigate the murder of a cruise ship entertainer, only to find themselves trapped at sea with the killer.

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 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 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 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.

Beckett and the 12th Precinct look into the murder of an English as a Second Language 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 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.

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.

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.

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.

After Hayley does a favor for an old friend, she finds herself implicated in a killing and cyber-terror attack. Now, Beckett and Castle must rush to solve the case and clear Hayley’s name.

When a mild mannered safety inspector for the city miraculously survives a poisoning, it might be luck; but when he survives another, it’s a mystery Castle and Beckett will have to solve.

After a movie star turned theater actor is mysteriously killed, Castle and Beckett go backstage and learn the star had more to worry about than just his lines.

When an axe-wielding, escaped psychiatric inmate drops dead in Castle’s P.I. office, Castle and Beckett’s investigation leads Castle to suspect the victim’s death could be the work of the Antichrist.

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.