Season synopsis
Contains spoilers for this season and earlier seasons.
Tommy survives the suicide attempt that closed the previous season, but the failed plot against Mosley has cost the family Aunt Polly: the IRA arranged her death and the assassination’s collapse. Michael blames Tommy and is sent to prison in Boston. Tommy tries to build a new future through the opium trade and a deal with Jack Nelson, while the growing fascist circle around Mosley and Diana Mitford keeps drawing him back into politics. His daughter Ruby becomes seriously ill, and the doctor tells Tommy she has tuberculosis.
Ruby’s illness worsens despite Tommy’s efforts to get her treatment, and she dies. Her funeral brings another surprise: Tommy learns that Duke, a young thief, is his son from a relationship before the war. He brings Duke into the family business. Arthur struggles with addiction but later returns to help Tommy; meanwhile Lizzie discovers Tommy’s affair with Diana and leaves, taking Charles with her. Tommy is also told he has an inoperable tuberculoma, supposedly connected to Ruby’s illness, and begins arranging his affairs as if he has little time left.
Michael is released and tries to kill Tommy with a car bomb, but Johnny Dogs has moved the bomb to another car. Tommy kills Michael after the bomb destroys the vehicle carrying his associates. The family sets a trap for the IRA, and Arthur kills Captain Swing, Polly’s murderer; Duke executes Billy Grade after Finn refuses to do it, and Finn is cast out. As Tommy prepares to die, Ruby appears to him and points him toward a newspaper image that places his doctor with Mosley and Diana. Tommy realizes the diagnosis was fabricated to drive him to suicide. He spares the doctor and rides away, alive and free of the false prognosis.