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 target of a manhunt that puts both of them in grave danger.
In "Get a Clue," Castle and Beckett investigatin the ritualistic murder of an accountant and learn there's more than meets the eye to her death.
Castle returns with a change of city and jobs for Kate Beckett. After saying "yes," Beckett moved to D.C. where her job with the AG's office isn't going as well as she hoped.
Beckett must use her wits to stay alive when she goes up against a powerful foe in "The Belly of the Beast."
Castle and Beckett discover that the victim of a building fire was actually shot to death, they get on the trail of a serial arsonist turned murderer.
The murder of a young video store clerk takes a strange turn when the team discovers his past history as a high-level hacker.
In "Like Father, Like Daughter," Alexis seeks the help of her dad to clear a man who's just 72 hours way being executed.
The strong start to the season continues with the exciting conclusion to "Valkyrie." The episode picks up immediately with Beckett telling Castle the bad news about being infected with the deadly toxin.
"Smells Like Teen Spirit" is a trip down memory lane for Castle and for fans as the episode restores some of the magic lost this season.
In "Number One Fan" Castle negotiates with a troubled murder suspect who claims she's innocent.