Soon after notorious New York gangster Joe Krozak brings his innocent wife Talya from Europe, they learn that she is pregnant. Despite his henchman "Curly's" warnings to go easy for a while, Joe has three of the Kile brothers, members of a rival gang, murdered. Although the police cannot find enough evidence to link Joe to the crime, he is soon arrested and convicted for tax evasion and sent to Alcatraz. Though all of his appeals fail and the warden at Alcatraz makes him realize that he is no longer a "big shot," Joe maintains his cocky attitude. When Talya comes to visit him with their new baby, she questions him about accusations made in the press, but he dismisses them and only seems interested in the baby. When she leaves, reporters harass her and one, Paul North, puts a gun in the baby's hand for a picture with the caption "Public Enemy No. 1, Jr." Desperate, Talya confronts Paul and his editor, but, while Paul is remorseful, his editor shows Talya information about Joe's crimes and she realizes the truth. The next time she visits Joe, she doesn't bring the baby. Joe is enraged and threatens her, but she tells him that she is going to change the baby's name and move away. Ten years later, after hard work and solitary confinement for prison troubles have weakened Joe, he is finally released. He is met by Curly who says that the "boys" need him to lead them again, but he soon discovers that Curly is only interested in obtaining any money that Joe had hidden over the years. Meanwhile, Talya has married Paul, who has since become an editor, and they have reared baby Joe as Paul, Jr. Their happiness over the boy's school award and a weekend camping trip is shattered, however, when Paul, Jr. is kidnapped by Curly's men who hope that seeing the boy will make the resistant Joe talk. Although the boy does not know who Joe is, and Joe pretends at first that he is uninterested, Joe's paternal feelings and pride at the boy's character give him the strength to break out of Curly's hideout. Although Paul, Jr. thinks that Joe is "mixed up" about thinking that he is his son, he is fond of Joe and willingly goes with him. They eventually go back to Talya and Paul's house and Joe lovingly puts Paul, Jr. to bed. When Talya thanks him for returning the boy, Joe tries to act as if he doesn't care, then leaves. Outside, Joe is confronted by Acey Kile, the brother of the gangsters whom Joe had ordered killed many years before. Acey threats to kill Joe have no effect until he says that he also plans to tell the newspapers Paul, Jr.'s true identity and ruin the boy's life. Joe then kills Acey, but is mortally wounded himself. As Joe dies, Joe's hand clasps Paul, Jr.'s school medal, "for outstanding achievement," which the boy had given to him.