Mike Sullivan is an enforcer for powerful Depression-era Midwestern mobster John Rooney. Rooney's son, Connor, is jealous of the close bond they share, and when Mike's eldest son, Michael, witnesses a hit, Connor uses the incident as an excuse to murder Sullivan's wife and youngest son. Forced to flee, Sullivan and Michael set out on a journey of revenge and self-discovery.

Two fathers: Michael Sullivan, a hit man for the Irish mob in Depression-era Chicago; and Mr. John Rooney, Sullivan's boss and the man who raised him as a son. Two sons: Michael Sullivan, Jr. and Connor Rooney, each desperate to earn his father's favor. Jealousy and competition put them all on a collision course, ultimately bringing Sullivan's work into his private life and leading to the death of his beloved wife and youngest son, Peter. Now Michael Sullivan and his surviving son are set on a journey instigated by tragedy and fueled by revenge.