An organized crime war breaks out between two rival gangs in Chicago during the Roaring Twenties. The leader of the Southside Mob is the notorious Al Capone, who resents his nemesis Bugs Moran's activity in the city. Moran, too, wants control of the town's bootlegging and gambling operations. His lieutenants Peter and Frank Gusenberg use threats and intimidation to make tavern owners do business with them in exchange for "protection." Peter Gusenberg also argues and fights with his moll, particularly over her extravagant spending of his money.