With the imprisonment of Al Capone for tax evasion, Frank Nitti has taken over the operation of the organization but that isn't stopping others from trying to muscle their way in. Arnie Seeger in particular thinks he has the opportunity to create a national crime syndicate and partners with St. Louis mobster Joe Kulak to make it happen. They plan on inviting key mobsters from across the country to a conference in Chicago. Into this mix comes a recently released small-time criminal, Maxie Schram.

Augie "The Banker" Ciamino (played by Keenan Wynn) is a vicious and brutal bootlegger who has developed a seemingly foolproof way of manufacturing liquor. He has equipped over a hundred immigrant homes with small stills to actually make the stuff and a unique way of collecting the product. Not everyone in the immigrant community is participating in the illegal liquor-making operation and Ness visits a night class where adults learn English, and writes his phone number on the blackboard.