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.