Beckett is faced with the toughest case of her career after finding Castle's car engulfed in flames.

While the team investigates the murder of a toy company CEO, Castle uncovers a lead to his mysterious disappearance, launching him into a dangerous investigation of his own.

When a pool shark is murdered by an unseen force, Castle and Beckett uncover evidence that the killer may have paranormal powers. Meanwhile, Castle and Beckett attempt to get their lives back to normal following his disappearance.

Beckett and Castle investigate the shooting of an ice cream vendor and clues lead them to suspect that an unknown second grade child might be able to help them solve the case; Castle goes undercover at a school to try and find the student.

When Castle gets knocked out while tracking some criminals with Beckett, he wakes up to a world in which he and Kate have never met.

When Castle and Beckett learn that a murder victim may have been poisoned at an Old West-style resort, they visit the resort posing as newlyweds to uncover the truth.

When Castle and Beckett stumble upon an activist as a prime suspect, the NYPD goes on a manhunt, and the consequences could be deadly for one member of the team.

After Castle finds out that his most beloved 1980's movie star has been murdered, he and Beckett receive aid from a group of older action heroes, and investigate the man's heavily guarded past in hopes that it will lead them to his killer.

Castle works for a mafia don to solve the murder of a mob doctor. Esposito has dinner with Lanie and her parents.

Castle becomes a Private Investigator and tries to solve a case before the precinct can.

While Beckett and her team investigate the murder of a young telenovela actress, Castle is hired by the show's star to follow the case from a different angle.

The NYPD searches for Beckett while 3XK calmly plays with them.

When an astronaut in a Mars simulation is killed, Castle and Beckett don spacesuits and enter the simulation to investigate. Much to their surprise, it seems no one inside and no one outside could have committed the murder.

A Hong Kong Detective works with Beckett and Castle on the murder of an ex-con turned tow truck driver.

Detective Ryan ends up in the middle of an assassination plot when he is on the security detail of a charismatic congressman; Castle and Beckett help Ryan investigate.

Beckett and Castle are faced with a large list of possible suspects when a personal injury attorney known as Richie "The Pitbull" Falco is murdered; a shocking secret deepens the mystery surrounding Richie's death.

A mysterious recurring dream drives Castle and Beckett to seek answers about the two-months he was missing. But their search for the truth has deadly consequences.

Beckett must help Castle and Alexis from the ground when the Air Marshal on their flight is found murdered in mid-air.

The creator of a sketch-comedy show is murdered, and the investigation yields a surprising secret.

A death occurs in the woods and Castle becomes obsessed with the case because it reminds him of a pivotal event in his childhood. Beckett reaches a turning point in her life.