Responding to an "Officer Down" emergency call, Castle and Beckett's latest case takes a shocking turn when it's revealed that the victim isn't a cop but a male stripper dressed up as one. The murder leads them into the world of male strip clubs, the hardships of struggling actors, and the price that people pay in pursuit of fame. Did our victim's dreams of stardom get him killed, or was there something more nefarious afoot?
Old wounds are reopened when the retired lead detective on Beckett's mother's homicide case contacts her with new information, but then is gunned down right in front of Beckett before he can tell her what he knows. The investigation into his death leads back to a decades-old conspiracy that may hold the answer to who was behind Beckett's mother murder and why. With the stakes and emotions running high, Castle and Beckett take their partnership to the next level.
During rehearsal for "Baron's All-American Beauty Pageant," the contestants are shocked to discover the body of Miss Illinois - strangled, but by whom? As Castle and Beckett delve into the cut-throat competition of the pageant world, they learn that a number suspects had motive for murder, including jealous fellow contestants, the pageant's larger-than-life millionaire sponsor, Victor Baron (Michael McKean, "Curb Your Enthusiasm"), and the show's host -- hedonistic TV personality.
While investigating the shooting death of her ex-partner in New York, Beckett comes to believe the suspect has fled to Los Angeles. Against orders, she travels to L.A., going renegade to track down the killer, with Castle unexpectedly along for the ride. As they dig deeper into the motives, they uncover a trail that leads from a rooftop pool in Hollywood to the sandy beach of Santa Monica. Along the way, they visit the set of the "Heat Wave" movie (based on Castle's book) and enlist the cast to help break the case. But as they get closer to apprehending the killer, Castle begins to wonder whether Beckett is out for justice -- or revenge.
When the body of a dockworker turned bar owner is found floating in the East River, Castle and Beckett's investigation takes them into the forgotten tunnels and passageways of turn-of-the-century New York, where they uncover a secret that's been buried since the days of Prohibition. The story celebrates New York bar culture, setting Castle on a quest to preserve history by buying a bar of his very own.
Castle and Beckett investigate the apparent robbery-homicide of a New York cab driver, only to discover that the victim was involved in a mysterious conspiracy with unimaginable consequences. As the stakes continue to rise, hard-charging federal agent Mark Fallon (guest star Adrian Pasdar) takes over the investigation. Together, Fallon, Beckett and Castle must race to unmask the truth about the victim before it's too late.
When a coded document hidden by a murdered bail bondsman gets Castle's imagination running wild, Beckett must steer the case back to the violent felons who populated their victim's world - only to discover that maybe Castle's crazy theories aren't so crazy after all. Complicating matters is the surprise arrival of Beckett's ex-partner (now a bounty hunter). As the two reunite over a history that Castle has no part of, Castle is forced to watch the relationship take a turn towards the romantic.
When a beautiful woman is found dead in an alley, all clues point to her being a victim of the notorious Triple Killer. The Triple Killer, or 3XK, terrorized New York City four years ago, then mysteriously disappeared. Now he's back. In a deadly battle of wits, Castle and Beckett race against time to stop 3XK before he claims his next victims. Lee Tergesen of "Oz" (as Marcus Gates, a violent felon and prime suspect in the serial killer investigation) and Michael Mosley of "Scrubs" (Gates' former cellmate) guest star in "3XK."
Castle & Beckett work the case of a man found dead inside a pizza oven, but it turns out not to be someone associated with the restaurant – it was a reporter. Was his story, “The Pizza Wars,” enough to get him killed, or was it something much deeper than that?
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.