Contains spoilers for this episode and earlier episodes.
Arthur Shelby's father returns with a proposal for a casino in America. Arthur wants to believe that the reunion offers him a future and gives him family money for the venture. Tommy and Polly distrust the visitor, who soon disappears with the cash. Arthur finds him at the railway station and learns that the grand business plan was a lie, leaving him ashamed and abandoned.
At the Garrison, Tommy faces IRA men who know about the stolen weapons. The meeting becomes a violent struggle, and Grace helps him survive. Her police work then reaches its objective: she identifies Danny's supposed grave as the place where the guns are buried. Campbell recovers the weapons, removing Tommy's bargaining power. Grace resigns her commission after the recovery, but rejects Campbell when he responds by asking her to marry him.
The police search for Tommy, who takes refuge in Grace's home. They become lovers, and he asks her to help with his life and business without knowing how she has helped Campbell. Elsewhere, Arthur attempts to hang himself after his father's betrayal but survives. Tommy gives him a business card naming him a partner in Shelby Brothers Limited. Arthur is offered a share in the family's legal operation while Tommy remains unaware of Grace's full identity.