November 1920. The Irish War of Independence is raging. IRA member Jimmy Mahon is recruited to Michael Collins' "Squad" and instructed to root out an informant. Codebreaker Ursula Sweeney, working in Dublin Castle, is "turned" to the rebel side.
Jimmy breaks Joey out of prison, and helps Ursula to be reunited with her son. Eithne's outrage at Diarmuid's death is ignored, and Maurice faces an impossible choice.
General Winter suspects Lily of being a spy, and Ursula must try to help her without implicating herself. Robbie plans to kill Eithne, but is stopped by an unexpected opportunity.
A price is placed on Ursula's head following the attack on General Winter's spy ring, and Jimmy confronts Brogan in the midst of the Bloody Sunday Massacre.