Bootlegger Ed Carson is sent to prison. His old gang turns from liquor (now legal) to kidnapping. When they nab the son and daughter-in-law of the judge who sent Carson to prison, he is paroled to help in the capture.

As the end of Prohibition nears, Edward Carson, the head of a bootlegging racket, angrily refuses to listen to the suggestion of his cohort, Chopper Allen, that they switch to the "snatch" racket, the kidnapping and holding of wealthy men for ransom. Carson reluctantly agrees with the scheme of his attorney, William Bennett, to plead guilty to an income tax charge so that, through Bennett's connivance, he will receive only a small fine and a suspended sentence. Reporter Jane Lee, who has won Carson's confidence, tells him that she intends to write his biography. He is excited, but he insists that she not write about the earlier kidnapping and murder of his daughter and the death of his wife, which soon followed. When Carson mentions that he plans to plead guilty to the federal charge, Jane, who knows of Bennett's involvement with Carson's mistress, Marilyn Kirk, warns Carson to reconsider. Carson pleads guilty nevertheless, and U.S. District Judge Thomas Penfield sentences him to five years imprisonment. In jail, Carson plans to get back at Bennett and instructs Chopper to spring him. Chopper and his men stop the train that is taking Carson to the penitentiary, but during the subsequent break and shootout, Carson learns that Chopper plans to murder him, so he gives himself up. Chopper then has Bennett and Marilyn killed off and, after beer is legalized, reorganizes the racket to commit kidnappings, which terrorize the nation. The gang is unstoppable because they use a different mob for each "snatch." Judge Penfield is appointed to head a president's commission for the suppression of organized crime, and he declares war against racketeers over a radio broadcast. When Carson, who has become a model prisoner, is questioned by members of the commission on his ideas for reducing crime, he impresses them with his knowledge of the operation of the racket and declares that if he were let out, he could break it up. He convinces them by relating his feelings about the kidnapping of his daughter and suggests that he have surgery done to change his appearance so that he can infiltrate the gang. The warden calls the attorney general and arranges for the plan to begin. Jane, who was touched when Carson earlier told her how nice it was to see their names together on the cover of her biography of him, is suspicious when the warden now says that Carson has died from an operation for appendicitis, knowing that he had his appendix removed five years earlier. Chopper has his hoods kidnap Judge Penfield's newlywed son and daughter-in-law. In response to a note from the kidnappers stating that they will release their captives if Judge Penfield stops his activities and goes to Europe, the judge broadcasts his refusal. After the newspapers publish the story of Carson's death in prison, he goes to see Chopper in disguise and says that he was Carson's cellmate. Carson then wins Chopper's confidence when he protects Chopper from a bullet shot through a window by his cohort, Butts McGee, and gets hit in the shoulder. The doctor who removes the bullet, however, informs Chopper that it was only from a .22 rifle, and Chopper becomes suspicious. Jane finds Carson in Chopper's office and recognizes him. After Carson is taken into a car by Chopper's men, he pulls a gun on them. Jane then gets in, and Carson pushes the gangsters out after he learns that the kidnapped couple are locked up in a sanitarium. Carson and Jane go there, and by viciously grabbing the doctor's throat, Carson makes him tell where the hostages are. Jane hides them as Chopper's car drives up. Chopper unsuspectingly goes into the hostage room, and Carson locks the door with them both inside. Chopper then realizes Carson's identity, and they both shoot each other as the police arrive and engage in a gunfight with Chopper's gang. Carson dies in Jane's arms, and she hugs him and cries. While the newspapers praise the unknown hero who died rescuing the couple, Jane and Butts clink beer mugs in a toast to "a pretty swell guy."