Season synopsis
Contains spoilers for this season and earlier seasons.
Castle and Beckett begin a relationship while trying to keep it hidden at the precinct. The investigation into Beckett’s mother’s murder leads to Senator William Bracken, whom she confronts with a threat to expose him if anyone she loves is harmed. Gates lets Beckett return to work after her suspension. Their attempts at discretion become increasingly awkward: a romantic Hamptons weekend turns into a murder investigation, and Ryan discovers their secret but keeps it to himself.
Jerry Tyson frames Castle for murder, forcing him to escape custody and prove that the serial killer is behind the evidence. Later, Alexis and her friend Sara are kidnapped and taken to Paris. Castle follows, discovering that Alexis is the real target of a plot against his own father. The intelligence operative calling himself Jackson Hunt reveals their relationship and helps Castle confront the kidnappers. What began as a missing-person investigation brings three generations of Castle’s family into the same danger.
Beckett’s work attracts an offer from the Attorney General’s office in Washington. She attends the interview without telling Castle, and the boarding pass he finds exposes a choice they have avoided discussing: whether her career can move forward without ending their relationship. Martha challenges Castle’s reluctance to commit, while Beckett talks through her fears with her father. At the swings, Castle asks her to marry him. Her answer remains unresolved as the season ends.