A new police chief goes after a gangster boss but is thwarted by his own brother, lawyers, and a violent shoot-out.
This movie is prefaced by a quote from President Herbert Hoover, suggesting that if policemen were glorified instead of criminals, then crime could be stamped out. Four murdered men are found hanging in a basement. Captain Jim Fitzpatrick (Walter Huston) arrests bootleg boss Sam Belmonte (Jean Hersholt) and four of his "guns," but they are soon released by a writ of habeas corpus. Jim is welcomed warmly by his wife, and his brother Ed (Wallace Ford) warns him about going after Belmonte. Ed is on the vice squad, and Jim asks for his help. Ed meets Daisy (Jean Harlow) in a line-up. Jim is unhappy about being transferred to the quiet suburbs, but his wife consoles him. Ed calls on Daisy to question her; they drink beer; she dances, and he kisses her. Jim and his buddies Tom and Mac answer a call to pursue bank robbers. Jim shoots one of them and is wounded in the arm.
Ed has told Jim nothing about Belmonte; but Jim gets appointed chief of police, is sworn in, and announces his plans to clean up the city and close the gin mills and speakeasies. Ed asks for a promotion, but Jim says he is not ready. While Ed and Daisy are in a speakeasy, Ed accepts a bribe from Belmonte for a way to bring in his "grapefruits." The press asks Jim about the police brutality petition; he says he is going after Belmonte. Jim asks Ed to guard a truckload of money, and his special agents Tom and Mac volunteer to help. Ed mentions the money to Daisy, who tells Pietro. She suggests Ed help them get the load of cash so they can go to France. Ed sends off two workers to eat and tells the robbers to hit him on the head. They take the truck and are chased by the police. After killing a kid and Mac, they are caught. Jim asks Ed to identify them, but Ed says he can't. While police pretend to torture one, Jim gets the other to say Ed tipped them off; Ed confesses and is arrested for murder.
Belmonte's lawyer skillfully defends the three men, and the jury finds them not guilty. Jim is up late when Ed comes in. Jim calls him yellow; but Ed agrees to tell Belmonte he'll spill everything to the press. Jim calls Tom to get twelve men. While people are celebrating, Ed slaps Belmonte and says he is going to spill. Jim and the cops come in and have everyone leave except Belmonte's gang. Ed is held hostage; but Jim is adamant. Ed is shot first, and then in the shoot-out Daisy, Belmonte, and Jim are killed along with most. Finally Jim's oath of office is heard again.
This shift of viewpoint from the gangsters to the police improves the moral perspective. Even though Jim is portrayed as a loving family man, his violent police methods still leave much to be desired in the crime wave stimulated by Prohibition.