Michael Sullivan, Sr. (Tom Hanks) serves as an enforcer for Rock Island Irish mob boss John Rooney (Paul Newman) during the harrowing times of the Great Depression. Raised by Rooney after losing his parents, Sullivan enjoys a special bond with him, even more so than that with Rooney's own son, the volatile Connor (Daniel Craig). The precarious balance is shattered when Connor, driven by paranoia, kills their disgruntled associate Finn McGovern in a confrontation that Sullivan witnesses. Unfortunately, Sullivan's twelve-year-old son, Michael Sullivan, Jr. (Tyler Hoechlin), inadvertently witnesses the chaos from the safety of his father’s car, which sets off a violent chain of events.
In a twist of fate, despite Sullivan’s desperate attempts to keep his son safe, Connor retaliates in a fit of rage by murdering Sullivan's wife, Annie, and their younger son, Peter, believing he has targeted Michael Jr. This horrific tragedy prompts Sullivan to seek vengeance, leading him to flee to Chicago in search of the infamous Al Capone and to track down Connor, who has gone into hiding. Sullivan's initial meeting with Capone's associate, Frank Nitti (Stanley Tucci), is fruitless, as Nitti is instructed to send the sinister crime scene photographer and killer Harlen Maguire (Jude Law) after him.
In a dramatic encounter at a roadside diner, Maguire fails to eliminate Sullivan but not before Sullivan smartly disables Maguire's car. As Sullivan takes to robbing banks tied to Capone and Rooney for funds to exchange for Connor, he takes the opportunity to teach Michael how to drive, ensuring he is prepared for the perilous getaway. As the mob begins withdrawing funds, Sullivan seeks help from Rooney's accountant, Alexander Rance, but finds himself betrayed when Maguire ambushes them. Thanks to Michael’s timely warning, Sullivan manages to escape, though injured.
Finding refuge on a farm with a childless elderly couple, Sullivan recovers and discovers shocking truths from the ledgers about Connor's deceitful embezzlement of his father's money. In a poignant moment of bonding, they express their gratitude by gifting the couple a significant portion of their stolen wealth. When Sullivan confronts Rooney at Mass with the knowledge of Connor's betrayal, Rooney, despite knowing the truth, refuses to forsake his son.
Under the cover of night, Sullivan systematically eliminates Rooney's henchmen before finding Rooney himself. In a somber exchange filled with emotion, Rooney expresses his gladness that it is Sullivan who has come for him, leading Sullivan to take the tragic step of ending Rooney's life. With Connor’s whereabouts now revealed by Nitti, Sullivan sets out for a final confrontation. He tracks Connor to a hotel and kills him, believing this to be the end of his troubles.
However, a sinister twist awaits as Sullivan is ambushed by the vengeful Maguire, who shoots him just as Sullivan has taken Michael to safety at his Aunt Sara's beach house in Perdition. Although Michael confronts the dying Maguire with a gun, he finds himself unable to pull the trigger. In a defining moment, Sullivan draws a weapon and takes down Maguire before succumbing to his injuries in his son's arms.
In the aftermath, Michael, heartbroken over his father's death, seeks solace with the elderly couple on the farm, reflecting on his father's fear that he might become like him. In a contemplative revelation, he vows that if anyone dared to ask whether his father was a good man, he would only say that he was, indeed, his father.
