The Untouchables S01E11 - You Can't Pick the Number

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.