Detective Kevin Ryan is on the security detail of a charismatic congressman attending a charity event when shots suddenly ring out. Driven to apprehend the killer, Ryan must revisit the events that led up to the shooting, with the help of Castle and Beckett.
When an ER physician is gunned down in the street, Castle and Beckett soon discover that the victim was a mob doctor to a Mafia family run by an old friend of Castle's. Also, against this backdrop of Christmas, Esposito and Lanie reach a defining moment in their relationship.
When a young Latin telenovela actress is murdered, Beckett and the team delve into a case that is as flamboyant and full of intrigue as any telenovela.
Castle and Beckett find themselves on opposite sides of the case when Castle's old school friend (guest star Jason Wiles) emerges as the prime suspect in his own wife's murder. As they work to solve the crime, Castle comes to realize that one of two terrible things must be true... Either Detective Beckett is about to arrest an innocent man for murder, or his old friend is a cold-blooded killer.
The investigation into the shocking death of a museum curator, crushed by a falling gargoyle, takes a bizarre turn when Castle and Beckett learn that he isn’t the first member of a recent archeological expedition to die. It turns out there was a legend inscribed over the burial chamber the team unearthed warning that “all who gaze upon the face of the mummy are doomed.” Was the curator just the latest victim of “The Mummy’s Curse”? And if so, what does that mean for Castle, who snuck a peek at the mummy when no one was looking?
As Halloween approaches, Castle and Beckett are called to a graveyard where the body of a young man sporting vampire fangs has been discovered with a wooden stake driven through his heart. Their investigation takes them deep into the heart of New York’s underground vampire fetish community, where they learn that the motive for the victim’s murder may be hiding within the pages of the graphic novel he was writing before his death.
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.
In the first of a two-episode story arc, Castle & Beckett begin a murder investigation that also exposes a plot to kidnap the daughter of a wealthy Middle Eastern businessman. Dylan Walsh ("Nip/Tuck") guest stars as FBI Agent Harris, an even-keeled professional brought in to help find the kidnappers.
When the owner of historic Drake's Magic Shop in New York is found drowned in Houdini's famous water torture tank, Castle and Beckett must delve into the world of magic, magicians and their secrets to find his killer. As part of their investigation, Castle & Beckett meet master magician Tobias Strange (guest star Gilles Marini, "Brothers & Sisters," "Dancing With the Stars"). Meanwhile, the magicians aren't the only ones keeping secrets, as a new romantic relationship is revealed for Esposito and Lanie.
When Castle and Beckett find giant footprints at the site of a vicious murder, the team is forced to confront the unlikely theory that Bigfoot is the killer. But as they trek into the world of primate research, big game hunting and mythological creatures, they realize that finding the man (or beast) responsible may put them on the endangered species list.