Beckett and her team burst into an apartment on a murderer's trail, just to be surprised when they see Castle, who they haven't heard or seen in months, standing over a dead woman's body holding a gun. Beckett, has no other choice but to arrest Castle until he proves his innocence.

Beckett and Castle look for the killer of a famous psychic while debating whether extrasensory abilities are real or not. When a letter arrives from the victim predicting her death they must determine who actually wrote the letter – the victim or the killer.

With the latest case of a murdered bail bondsman, Beckett discovers that Castle's wild imagination and theories may be on the mark. Beckett's ex-partner makes a surprise arrival and Castle is forced to watch the two reminisce and engage in a little romance.

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?

An unknown woman falls out of a casket along with the original deceased when pallbearers lose control of the casket at a funeral and the investigation takes Beckett and Castle into the world of amorous, bed-hopping physicians.

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.

An "Officer Down" call turns out to be a male stripper dressed like a cop. Castle and Beckett explore the world of male strip clubs and struggling actors, all people in pursuit of fame. They need to determine if the murder was because of the victim's dreams of stardom or something more sinister.

Castle and Beckett investigate the murder of an NYC subway worker found shot in Central Park. But, while investigating the murder they uncover the abduction of a young boy as well. The team must determine the motives behind the high stakes kidnapping in order to save the young boy's life.

Castle's latest theory is alien abduction after an astrophysicist's death is found to be from explosive decompression. A well know alien abduction expert gets involved in the case. To complicate things more, a government agent wants to shut down their investigation.

Castle and Beckett investigate the murder of a dockworker turned bar owner who's body is found floating in the East River. In the process of the investigation they uncover a secret buried since the days of Prohibition.

When Castle's novel "Heat Wave" is turned into a movie, actress Natalie Rhodes, shows up at Beckett's invitation to better understand the character she's going to play. Meanwhile, the threesome investigate the murder of a high-class matchmaker.

Castle and Beckett investigate the murder of the owner of a historic magic shop found dead in a Houdini's water torture tank. Meanwhile, Lanie and Esposito are trying to keep their relationship secret and Castle ends his relationship with Gina.

When the detective who investigated Beckett's mother's murder is shot before Beckett's eyes before he can give her new evidence in the case, Beckett's old wounds are reopened. The investigation of the detective's death leads the team to an old scheme which may provide the answer to why Beckett's mother was murdered and who ordered it.

The brutal murder of a lottery winner has Castle and Beckett up to their eyeballs in suspects, envious and angered by the victim's sudden move from the poorhouse to the penthouse. As the precinct buzzes with fantasies of what our cops would do if they won the lottery, Martha struggles with the reality of such a decision when she suddenly inherits money she feels she doesn't deserve.

Castle and Beckett find themselves on opposite sides of the case when Castle's old school friend 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.

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.

With time running out, Castle and Beckett must put aside their differences with Agent Fallon to avert a city-wide catastrophe.

Castle and Beckett investigate the axe murder of the head writer for a long time New York soap opera. Everyone is suspect when it's discovered that the action behind the scenes plays out as good as the on-air storylines.

When a juror dies during the high profile trial of a murdered socialite, Castle and Beckett discover that the juror wasn't really as perfect as he appeared to be.

When a reporter is found dead inside a restaurant's pizza oven, Beckett and Castle go to work on solving the case. They must figure out if his story "The Pizza Wars" is what got him killed or if there's something more to the story.

When a champion swimmer and Olympic hopeful is found dead in a training pool, Castle and Beckett dive in to investigate his murder, and uncover myriad secrets that might have led to his death.

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.

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, and the show's host -- hedonistic TV personality, Bobby Stark.

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.