Tom Reagan is the right-hand man for Leo O'Bannon, an Irish mobster and political boss who runs a U.S. city during Prohibition in the United States. When Leo's rival, the Italian gangster Johnny Caspar, announces his intent to kill Bookmaker Bernie Bernbaum, Leo goes against Tom's advice and extends his protection to Bernie. Bernie is the brother of Verna, who has begun a relationship with Leo – while also carrying on an affair with Tom.