Nothing is as it seems when Castle and Beckett investigate what appears to be the assassination of an intelligence operative. Meanwhile, Beckett's romance with Demming threatens her relationship with Castle, forcing them to confront their feelings for each other.
When Castle appears on a late-night talk show to promote his book, Heat Wave, legendary host Bobby Mann (guest star Tom Bergeron) leans in during a commercial break and whispers, “They want me dead.” When Mann dies later that night, seemingly of natural causes, Castle has to convince Beckett that there was foul play. During the investigation, Castle is seduced by a Hollywood hottie (guest star Kelly Carlson), who was the other guest on Bobby Mann’s show the night he died.
When two separate murders are committed on the same night, Castle wagers Ryan and Esposito that he and Beckett will solve theirs first. The frenzied race to catch their respective killers and win the bet leads each investigative duo to a likely suspect, only to find that they both have airtight alibis. But bizarre twists in both cases force the two teams to work together to unravel the mind-bending mystery behind each murder
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.
When an Arctic explorer is killed during a polar expedition, the mysterious circumstances of his death take Castle and Beckett from the penthouses of Park Avenue to the halls of the CIA. But Castle’s delight at the case’s many twists and turns soon turns to frustration as he realizes that their elusive killer might just be fooling them all.
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.
When an art dealer is gunned down in his gallery, Castle & Beckett discover that a bullet is inexplicably missing from the crime scene. The mystery is deepened by an amnesiac who witnessed the crime but can’t remember what he saw or even who he is.
In the special two-part storyline, Dana Delany (“Desperate Housewives”) plays Federal Agent Jordan Shaw, an insightful and accomplished Federal investigator who teams up with Castle & Beckett to hunt down a cunning and elusive serial killer. This will reunite her and Nathan Fillion, who played Dr. Adam Mayfair, the younger husband of Katherine Mayfair (Delany) on “Desperate Housewives.”
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.
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.