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.
Castle is hired to uncover whether a client's husband is having an affair, but the case takes a shocking turn when Castle witnesses the client's murder - by her husband. But with no proof that the killing took place, Castle and Beckett must investigate to expose the truth.
The serial killer Jerry Tyson, known as 3XK, is back and Castle and Beckett find themselves face-to-face with him at the precinct. Can they put him away for good?
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.
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.
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.
Beckett receives a tip and ends up launched into a fight for her life with mercenaries on her trail. Castle tries to figure out why his wife is on the run.
Castle poses as a college professor so he can investigate the gruesome murder of a student while trying to win back the love he thinks he lost in Beckett.
When Castle's idol, a famously reclusive author, turns up dead, Castle is determined to solve his hero's murder. But as he and Beckett dig deeper, they discover that truth is stranger than fiction.
When a priceless work of art is stolen and its transporter murdered, Castle and Beckett must work with the key witness to track down the painting and sniff out the killer.
While Beckett is out of town, Castle becomes involved with Detective Slaughter in a case where a hi-tech chip has been stolen and one of Slaughter's informants is murdered.
In order to hunt down the brutal murderer of a grifting seducer, Castle and Beckett must investigate New York's elite. Meanwhile, Castle plans to surprise Beckett on their one-year wedding anniversary.