Season synopsis
Contains spoilers for this season and earlier seasons.
Castle returns to the precinct after investigating Beckett’s mother’s murder without her permission. She is angry, and the first case forces them to work together again while Castle tries to repair the damage. Beckett makes the terms plain: if she asks him to leave after this case, he must go. Castle agrees, apologizes for crossing that line, and proves useful as their investigation moves from a stolen corpse into Chinatown’s drug trade, Russian gangsters and an underground poker game.
As the partnership settles back into its familiar rhythm, Castle’s work on Heat Wave and their separate personal lives keep exposing feelings neither one names. Beckett is unsettled when Castle reconnects with Kyra, an old girlfriend who is about to marry, while Castle notices Beckett’s interest in another detective. Their investigations range from a murdered assistant district attorney to a serial-killer case with the FBI, where Beckett and Castle follow evidence across multiple attacks and survive the threat at Beckett’s apartment. In the finale, Beckett breaks up with Tom Demming and prepares to tell Castle how she feels, but he leaves for the summer with Gina, his ex-wife and publisher.
The season’s most personal turn comes when a gang-enforcer murder leads Beckett and Castle back to her mother’s case. Lanie and a forensic expert connect evidence to Dick Coonan, a philanthropist who is also the assassin known as Rathborne. Coonan admits he murdered Johanna Beckett, then takes Castle hostage; Beckett shoots him to save Castle before he can name the person who ordered the killing. The immediate murderer is dead, but the larger conspiracy and the reason behind Johanna’s death remain unresolved.