Eliot Ness and the Untouchables set their sights shutting down the numbers racket. The numbers are like a lottery where anyone can place a bet of up to one dollar on a three digit number. The payout for a full dollar bet is $600 so the profit for the mob, who run the racket, is the remaining 40%. Ness wants to shut down that cash flow which can be used for more heinous crimes. 

With Al Capone out of the way, the mob is looking to relocate its base of operations outside of Chicago in a nearby community. Their first step is to get rid of the incorruptible mayoral candidate, Judge Leon Zabo, who they run down in the street. The Coroner's inquest is a sham and it is obvious that the Chief of Police, who appoints the Coroner, is already in the syndicate's pocket.