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.

When a priceless work of art is stolen and its transporter murdered, Castle and Beckett must work with the key witness to track down the painting and sniff out the killer.

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.

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.

Beckett og teamet etterforsker drapet på en politimann ved New York politihøyskole. Castle må ta et valg som vil få store konsekvenser for ham og Beckett.

Beckett og Castle finner et spor på et åsted som fører dem til en av Espositos gamle saker. Men det oppstår komplikasjoner når de oppdager at Esposito ikke har fortalt dem alt om sin fortid med gjerningsmannen.

Drapet på en mann med forbindelser til smugling av tyrkiske fornminner sender Castle, Beckett og teamet på jakt etter Aladdins lampe, i håp om at den kan føre dem til drapsmannen.

Når Hayley gjør en tjeneste for en gammel venn, blir hun samtidig innblandet i et drap og et cyberangrep. Beckett og Castle må løse saken for å renvaske henne.

En av byens sikkerhetsinspektører blir forgiftet, men overlever på mirakuløst vis. Når han overlever nok et drapsforsøk, er Castle og Beckett fast bestemt på å løse saken.

En filmstjerne som prøver seg som teaterskuespiller i et Shakespeare-stykke blir drept på mystisk vis, og Castle og Beckett går bak kulissene for å løse saken.

En psykiatrisk pasient på rømmen faller død om på Castles kontor, og Castle mistenker at gjerningsmannen er selveste antikrist.

Castle og Beckett får instruksjoner om å levere en minnepinne til Loksats revisor, men en uforutsett hendelse setter etterforskningen og livene deres i fare.