A robbery-homicide prompts Beckett to invite Demming to assist on a case, giving Castle a ringside seat to their budding romance. When it becomes clear that the two men have very different ideas about how to proceed, the investigation becomes an unspoken competition for Beckett's attention, one in which each man races to solve the case, as Beckett referees between her two admirers.
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?
Castle and Beckett investigate the hit-and-run death of a bike messenger, brutally murdered to prevent him from delivering a package, the contents of which could free a wrongly convicted man from prison. In a surprising twist, this tragic death is linked to a murder case that Captain Montgomery investigated a decade earlier. To solve the present murder, Castle and Beckett must dredge up the past by uncovering the secrets and scandals of a prominent New York family.
The murder of an Assistant District Attorney thrusts Castle and Beckett into the world of ex-cons and escorts. But when Castle’s desire to help a vulnerable call girl endangers the case, Beckett is forced to decide between honoring promises and putting a killer behind bars. Matters are complicated even further when Castle’s daughter shares a potentially explosive secret with Beckett instead of her father.
When Castle and Beckett are called to a wedding to investigate the death of a bridesmaid, Castle is stunned to discover that the soon-to-be bride is his old flame, Kyra, “the one that got away” (guest starring Alyssa Milano). Complications ensue as Kyra, caught off-guard by Castle’s reappearance in her life, wonders if she’s marrying the right guy. With the nuptials forestalled and the entire wedding party under suspicion, Beckett questions Castle’s ability to be objective about the case. But when it looks to Beckett like Castle and Kyra might rekindle their romance, her judgment may be compromised as well.
Investigating the murder of a thief, Castle and Beckett are surprised to learn that Esposito has a personal connection to the suspected killer. Another surprise is in line for Castle when Beckett hits it off with the handsome Robbery detective assigned to the case, Tom Demming (Michael Trucco in a recurring role rest of season). Now this romantic triangle must work together to solve the case.
When a murdered man is found stuffed in the garbage chute of an apartment building and two women arrive to ID his body — one his wife and the other his fiance — Castle and Beckett have their hands full keeping the women from killing each other as they work to peel back the layers of the victim’s double life. Was it a jilted woman, corporate espionage, or a much darker secret that led to his demise?
Castle’s book agent, Paula Haas (guest star Debi Mazar), approaches him with a career changing opportunity, but taking it would mean the end of his relationship with Beckett. Will the murder of an unidentified woman found dead in a manhole be their last case together?
A beloved former major league baseball player is found dead after a goodwill trip to Cuba. The investigation, which includes running into Joe Torre (guest starring as himself), leads the detectives into New York’s Cuban community to solve the murder. Meanwhile, Alexis’ genealogy project forces Castle to consider the identity of his unknown father.
When a half-naked woman is found covered in caramel sauce and hanging by bondage cuffs in a public park, Castle and Beckett’s investigation takes them into New York’s underground world of sexual domination. Naturally the case serves as sexy fodder for their already charged relationship banter.