Author Richard Castle joins NYC Detective Kate Beckett to help solve the case of a serial killer who is reenacting murders from Castle's novels; Castle becomes very intrigued with the murders and continues to shadow Beckett, much to her chagrin.

When a teenaged boy whose family has recently fallen on hard times is found dead in a boat in Central Park, Castle and Beckett must piece together the mystery behind the boy's final moments. Meanwhile, Castle mulls over leaving Martha home while he chaperones Alexis' trip to Washington, D.C.

The investigation behind a body found wrapped in a rug on the sidewalk leads Castle and Beckett deep inside the world of New York City politics. The partners discover a world of expensive escorts, arrogant tycoons, corrupt investigators, and the effects of betrayal.

When the new season begins, Castle is wrestling with how to repair his relationship with Beckett, while struggling to finish his soon-to-be-published bestseller, Heat Wave. But circumstances force the pair back together to investigate the mysterious murder of a man found dead, tangled in the limbs of a tree.

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.

An up-and-coming rock star's body is found in a scene that appears staged from her recent music video.

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.

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 Beckett and her team burst into an apartment on a murderer's trail, they see Castle standing over a dead woman's body holding a gun; Beckett arrests Castle as he asserts his innocence.

Castle and Beckett look into the murder of a young mathematician gunned down with a 200-year-old bullet, sparking some wild theories by Castle about a time-traveling killer. When their investigation uncovers a tricked-out DeLorean and a suspect in Victorian clothing, is it possible Castle's crazy idea has some validity? This winding tale twists through the towers of Wall Street and into the world of a secret steampunk society that embraces the romance and simplicity of the past, while coupling it with the hope and promise of the future.

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 takes over the investigation. Together, Fallon, Beckett and Castle must race to unmask the truth about the victim before it's too late.

Kate Beckett's investigation into her mother's death is reactivated when Hal Lockwood - a professional hitman with knowledge of Beckett's mother's murder - stages a spectacular escape during a court hearing. As police launch a manhunt for Lockwood, Castle and the team uncover evidence of a deeper conspiracy involving a mysterious figure with law enforcement connections who is linked to both Lockwood's escape and the killing of Johanna Beckett. The search for Lockwood and the quest to identify his co-conspirator leads to a shocking and deadly conclusion.

Detective Beckett fights for her life as Castle, plagued by guilt over his role in the events, struggles to uncover who's behind her brutal shooting. Meanwhile, back at the precinct, Ryan and Esposito have to adjust, as Victoria "Iron" Gates becomes the precinct's new uncompromising Captain.

While investigating the mysterious shooting death of a young woman, Castle and Beckett face a cop's worst nightmare when they discover that the gun used in the killing is Det. Ryan's old service weapon - the one that was stolen by the serial killer, 3XK. Now with the clock ticking, the team must work to solve the murder, track down 3XK and retrieve Ryan's gun before the killer strikes again.

Castle & Beckett race to find the "Linchpin" in order to stop the first domino in a chain of events which will plunge the United States into war. Their efforts continue to put Castle in contact with Sophia Conrad - a smart, commanding and sexy CIA operative who was Castle's inspiration for Clara Strike in the "Derrick Storm" series of books; and intelligence officer Martin Danberg is back.

When the murder of an Army veteran puts Beckett on the trail of the man who shot her, Castle must decide how much he's willing to sacrifice to keep her safe. As secrets are revealed and feelings are put on the table, the lives of the detectives at the 12th Precinct may never be the same.

Picking up the morning after, Castle and Beckett now have to decide if they're a couple or was it just a onetime deal. But before they can tackle that, they must deal with those responsible for Kate's mother's death who are now a threat to Beckett.

Castle and Beckett’s plans for a romantic weekend in the Hamptons are interrupted when a dying man stumbles into Castle’s backyard, collapsing into his pool. Unable to escape the lure of the investigation they join up with the small town’s well-intentioned, but inexperienced sheriff to find the killer,

In the powerful conclusion of a two-episode story arc, when the FBI fails to get his daughter back, Castle takes matters into his own hands, reaching out to a shadowy fixer to help him recover Alexis. But Castle soon learns that his daughter's kidnapping may be part of an even more sinister agenda.

A grisly murder investigation leads Castle and Beckett to a suspect who claims he's traveled back in time to stop terrible events from unfolding, events that will change the course of human history. Is he simply a deluded killer, or is it possible that he's telling the truth?

Castle and Beckett arrive at a crime scene to discover that the female victim bears a shocking resemblance to Medical Examiner Lanie Parish. As the team tries to make sense of this mystery, they realize the killer may be targeting detectives of the 12th Precinct. Dr. Kelly Nieman, an exclusive Manhattan cosmetic surgeon who draws Castle and Beckett's interest because of her connection to the victim.

Beckett is recruited to assist on a Narcotics investigation, but a routine mission turns deadly when an undercover operation goes array. To survive, Beckett must engage in a battle of wits against some of the most dangerous men in the New York underworld – including a powerful enemy from her past.

A secret investigation conducted by Beckett related to her mother's murder goes awry when a man she has been surveilling is killed. When evidence links Beckett to the victim, she and Castle become the targets of a manhunt that puts both of them in grave danger.

Beckett is called to an accident scene to find Castle's car in a ravine, engulfed in flames.

When an ice cream vender is shot, evidence leads Beckett and Castle to believe that an unknown second-grader may have vital information about the case. Castle goes undercover at an elementary school to try and identify the second-grader but nothing goes as planned.

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.

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 a recruit officer at the NYPD Academy is killed, Beckett and the team go back to their old training ground to investigate. Meanwhile, Castle must reckon with a decision with profound consequences for him and Beckett.

With their best lead in hand, Castle and Beckett are ready to take on LokSat. But an unforeseen twist puts their case – and their lives – in jeopardy.