Chicago, 1931. Eliot Ness and his men had cracked the bootleg empire of Al Capone, by smashing his breweries and speakeasies. But now, thousands of gallons of alcohol were coming into the city from an outside source. Ness meets with D.A. Beecher Asbury; it doesn't take Sherlock Holmes to figure out where the booze is coming from, they've found 5-gallon cans with "Brawley Mills, Brawley, New York" stamped on them. Chemical analysis showed the stuff is 190 proof, no doubt produced under U.S. Government permit-- but it contained no denaturant, so it is safe to drink. Ness goes to New York, and takes Enrico Rossi and Cam Allison with him.
Ness meets with John Carvell, Federal D.A. in New York. They know Brawley Mills is making the alcohol legally, so now it's a matter of checking out 52 warehouses that store and ship the stuff; that takes 3 days. Rico finds out a lot of the alcohol is shipped by United Trucking Services; Ness says that's owned by Tommy Haynes, a crooked and powerful politician who protects Johnny Torrio. Ness meets with the president of Brawley Mills, E. Carlton Duncan, and the vice president, Brooks Wells. Duncan tells Ness that the alcohol is used for vanilla and lemon extracts, and such. They sell their excess alcohol to drug, perfume and cosmetics dealers. But that amount is 500,000 gallons, which nets them $5-million annually. Ness points out that could be cut to produce $100-million of booze for bootleggers. Duncan says, what the customers do with it after they sell it to them is their business.
Ness has government agents go over Duncan's books. Then Ness finds out about a shipment of 10,000 gallons of alcohol going to the Lorelei Perfume Co. in Chicago-- a front owned by Al Capone. Ness and his men fly back to Chicago. At night, Ness is there when a Capone truck pulls up; riding in the truck is Guillermo Torrio, Johnny Torrio's nephew. When the United Trucking truck goes inside, Ness and his men raid the place. There's a big shootout with guns, shotguns and choppers. There's one casualty: Guillermo Torrio-- and when his uncle in New York hears about it, he's plenty mad.
Ness and his men fly back to New York. Johnny Torrio roughs up Duncan, he figures he tipped off Ness. But Wells tells Torrio it was the books that tipped Ness. Torrio lays down his demands: Duncan is to pay 100 Gs to Guillermo's mom; and from now on, instead of 150 grand, Duncan has to pay him 300 grand per month. Duncan protests that he's already paid him $30-million of the company's money.
When one of Torrio's boys spots Wells talking to Enrico, he reports it; Torrio has Wells rubbed out. Later, Duncan tells Torrio he wants out; Torrio says he can't quit the rackets, and then demands $1-million in 24 hours. Meanwhile, fingerprints taken from Wells lead Ness to his real identity: he was Demos Brittano, who did time for swindling and embezzlement back in 1916. His brother also did time: Aristide Brittano who is now going by the name E. Carlton Duncan. Even though that was 15 years ago, Duncan could still face additional jail time, and he has been paying blackmail for 15 years-- to the tune of $30-million of the company's money. Ness, Rico and Cam intercept Duncan at his house, just as he is about to skip town with a suitcase full of money. Ness tells Duncan he'll have to testify to the grand jury.
Just then, 3 of Torrio's boys drive up, armed with choppers; they have orders to kill Duncan, Ness and his men. Duncan makes a run for it, he gets shot down. In the shootout, Ness and his men kill all 3 hoods. Duncan's suitcase spills open, and dollar bills are strewn all about by the wind. Ness had stopped the flow of alcohol from the East Coast to Chicago, and saved Brawley Mills from bankruptcy.