Bootleggers gain control of a town and move into the city; but those still alive are eventually caught by an undercover investigation.
Stockyard worker Louis Scorpio (Wallace Beery) and his rod are hired by bootlegger Johnny Franks (Ralph Bellamy). Jimmy Delano is warned not to sell alcohol to a rival gang, and the cops raid the still. Franks and Scorpio escape and tell Richard Newton (Lewis Stone) that Delano was arrested. Scorpio and Johnny are paid for bootlegging. Joe Colimo (John Miljan) sends his gang after Franks. Amid shooting Franks and Scorpio are chased in a car but return to Newton. Franks sends Scorpio for a load. Colimo with his gang comes in and asks who got his brother. Franks tells him where he can find Scorpio. At the dock Scorpio is shot but makes it back wounded. He finds his bottle of milk in the waste-basket and kills Franks. Newton hides Scorpio's gun before the police come in. Reporters Hank Rogers (Johnny Mack Brown) and Carl Luckner (Clark Gable) call in the story and flirt with waitress Anne Courtland (Jean Harlow).
Scorpio takes over Franks' business and gives Carl a present of money. Scorpio promotes Nick Mizoski (Paul Hurst) for mayor, and he wins. Colimo calls on Scorpio and suggests they work together. Mizoski fires police chief Donlin (DeWitt Jennings). Anne tells Scorpio that she is going to marry Hank. Scorpio offers Hank money, but he declines it and rejects Anne too. Colimo is murdered. Scorpio plans to move into the city with bootlegging. He learns some stills were closed when his weekly income decreases. Carl is helping the District Attorney, who has formed the "secret six" men in masks. Hank examines the bullets that killed Franks and Colimo, learning both were from the same gun. Hank searches and finds Scorpio's gun. Scorpio sees Hank, but Carl says he invited him. Hank takes a train, and Anne catches it to warn him; but Hank is shot dead. At the church service police arrest Scorpio.
Carl warns Anne not to testify. Scorpio is denied bail, and police question the formerly dumb Metz (Murray Kinnell). Metz testifies against Scorpio, though Newton shows that Metz is a wanted criminal. Anne testifies that Scorpio said he was going to kill Hank. Newton brings out that she got gifts from Scorpio. Scorpio tells Eddie not to let Anne get away. The jury, apparently bribed, finds Scorpio not guilty. Carl calls the law on Scorpio, but he is brought to Scorpio and is asked who are the secret six. The police close in, and Newton orders men to shoot Donlin. Carl breaks free and grabs a gun. Donlin is shot first. Scorpio demands money from Newton and shoots him for it. Scorpio climbs into Peaches' window, and she locks him in her closet. Carl and the police arrest him.
This gangster melodrama is based on the rise and fall of Al Capone, who took over a Chicago suburb before moving into the city. Acquitted for murder, he was eventually imprisoned for income tax evasion.