Notorious gangster Al Capone (Rod Steiger) begins his career as a low-level thug, but by knowing whom to betray and whom to reward, he becomes the mastermind of a criminal empire. Capone always gets what he wants, including the love of the beautiful Maureen Flannery (Fay Spain), a young widow whose husband was one of Capone's victims. Capone convinces other gang leaders to run the crime syndicate as a business, but his brutal methods earn him enemies dangerous to his future.