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

The episode was rated 8,05 from 678 votes.

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.

The episode was rated 8,06 from 696 votes.

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.

The episode was rated 8,07 from 740 votes.

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.

The episode was rated 8,08 from 678 votes.

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.

The episode was rated 8,10 from 748 votes.

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

The episode was rated 8,12 from 724 votes.

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.

The episode was rated 8,14 from 822 votes.

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.

The episode was rated 8,25 from 729 votes.

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.

The episode was rated 8,27 from 722 votes.

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.

The episode was rated 8,28 from 771 votes.

When Castle's novel ''Heat Wave'' becomes a movie, actress Natalie Rhodes accepts Beckett's invitation to visit and learn about the character she will play; Natalie observes Castle and Beckett's investigation of the murder of a matchmaker.

The episode was rated 8,34 from 763 votes.

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.

The episode was rated 8,40 from 776 votes.

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. Beckett and Castle's relationship takes a new turn.

The episode was rated 8,49 from 770 votes.

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

The episode was rated 8,55 from 782 votes.

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.

The episode was rated 8,61 from 791 votes.