Based on a novel by Armitrage Trail, a Capone-like figure gains underworld power with violent methods.
A written preface claims this film depicting actual occurrences indicts gang rule and government indifference to menaces of public safety, and it asks the audience what they are going to do about it.
When Louis Costillo is murdered, an editor predicts a gang war for control of illegal liquor. Costillo's bodyguard Tony Camonte (Paul Muni) is arrested, won't talk to cops, and is soon released on a habeus corpus writ. Tony visits Johnny Lovo (Osgood Perkins) and Poppy (Karen Morley). Lovo pays Tony. Tony jealously tells his sister Cesca (Ann Dvorak) not to let men kiss her, and he gives her money. Their mother pleads with Cesca not to be bad like Tony. Lovo takes over Costillo's gang, and Tony beats up a man who tries to leave. Tony and Rinaldo (George Raft) make men buy from them by bombing and shooting those who don't, even going to a hospital to finish off a wounded man. Tony invites Poppy out, but she brushes him off. Lovo reprimands Tony for going into the northside, and a corpse thrown from a car has a note with the same message. Tony's secretary can't even write. Tony gets a flower from Rinaldo which he passes to Poppy, who says O'Hara was killed in his flowershop (apparently by Rinaldo). The cops take Tony in, but again he is soon released.
Gaffney (Boris Karloff) brought in machine guns, and a drive-by shoots at Tony and Poppy in a restaurant. A wounded Lovo complains to Tony for getting rid of O'Hara. Tony takes over from Lovo with a machine gun. Seven men are lined up and shot on Valentine's Day. Gaffney tells the cops it was done by men dressed as police. Gaffney and Lovo are hiding out. Police say children are being killed in the streets. An editor argues news coverage is needed and calls for guns to be outlawed to stop organized murder. Gaffney is shot while bowling by Tony's gang. Tony joins Lovo and Poppy at a nightclub and dances with Poppy. When Tony sees Cesca dancing, he jealously takes her home and hits her. Tony is shot at from cars and is driven off the road. He and Rinaldo suspect a pleading Lovo; Rinaldo shoots him. Tony tells Poppy to pack, and Cesca tells Rinaldo Tony has gone away for a month. Tony returning asks his mother where Cesca is. Cesca is happy with Rinaldo; but the jealous Tony kills Rinaldo. Cesca says they were married and calls Tony a murdering butcher. The police come after Tony and shoot his secretary. As the police surround him, Cesca arrives with a gun. Tony shoots while she loads until she is shot. Tony is afraid to be alone, and she dies. Tear gas forces Tony to surrender; but he runs outside and is shot dead.
This film seems to be condemning violence at the same time it is making money using it as entertainment. Tony is exposed as a brutal killer who destroys himself and all those around him except his mother and Poppy. The only suggested solution of banning guns is heeded by no one.