Chicago, after the Repeal of Prohibition. With booze legal, the racket czars step up their dealings in narcotics. Ness and Lee Hobson are chasing two dope-pushers, one of them is Benny Rivas. After a shootout, one hood is dead. Benny moans, "Get me a priest." Ness finds heroin on him. Wanting to die with a clear conscience, Benny says, "808" and dies. That leads Ness to Maggie Storm's 808 Club.
Maggie runs the 808 Club and she's the featured entertainer. Ness had raided her during Prohibition. Maggie--who bears no grudge against Ness, in fact she likes him, tells Ness she is running the club for a Mr. Charles Banner. Maggie says soon she will be Mrs. Charles Banner. Ness points out to Lee Hobson that half of the big-time operators in town are in the crowd and there are a lot of out-of-town bigshots, too. After Ness leaves, the waiters mingle with the customers and read off some interesting items on the menu: 10 kilos of heroin, $110,000 in counterfeit bills, etc.; the customers discreetly bid on the items. Maggie tells her associate "Lucky" Quinn they'll turn $500,000 in business that night; 10% of the take is hers: $50,000.
In New York, a top boss of the NY Syndicate doesn't like it that Maggie's club in Chicago is operating outside of the Organization so he tells Louis "Lepke" Buchalter to acquire the club. Lepke sends his boy Vince Shirer to Chicago to pay Maggie a visit. Maggie knows that she, as a woman, would be pushed around by hoods, so she's always telling people that Mr. Charles Banner is running things. But Banner is always "out of town" or he's "just stepped out" it seems. Meanwhile, Ness sets up a sting operation. He's gotten small-time crook Ed Harker an early parole and gets him to peddle illegal tax stamps through the club. When Shirer tells Maggie about the sting, she sends Lucky Quinn to intercept the buying hood, Arnie Mallock. But Shirer goes to the warehouse too and kills Quinn with a knife. Later, Shirer tells Maggie he is taking over Quinn's old job.
Maggie doesn't want any more killings so she gives Shirer $25,000 to pay off Harker. But when Shirer meets Harker on a 3:30 a.m. train, Shirer sticks him with his knife and Shirer pockets the money. That night, an angry Ness drops in on Maggie. It seems the death of Quinn doesn't bother him so much, but he's taking the death of Ed Harker personal. Later, Shirer tells Maggie he's her new partner. There is no Charles Banner. He was her husband but Banner died in 1928. Shirer tells her to go meet her new boss. In Banner's office there is Lepke Buchalter. Lepke spells it out: 50% for the Organization, 25% for Shirer, and 25% for Maggie. She has no choice.
Ness goes to the 808 Club after it's closed. He wants Maggie's records. Ness knows she's a decent person. She only used to run a speak. Now, these mobsters have pushed her into a racket involving narcotics and murder. But when Ness can't promise she won't have to do prison time, Maggie balks. Later, an angry Shirer demands to know from Maggie what she was talking to Ness about. Maggie is shocked to hear that Shirer will be doing more killings. Later, when she listens in on the extension phone and hears Shirer talking to Lepke, she fears she will be killed. She grabs the books, calls Ness, and goes to her apartment. Lepke tells Shirer to rub her out.
Ness and Hobson speed over to Maggie's apartment. Shirer sticks her in the back with his knife. When Ness and Hobson get there, Shirer throws his deadly knife at Ness but misses as Ness shoots him. Maggie collapses in Ness' arms. Maggie spent 6 weeks in a prison hospital and served a ten year term. Maggie spent the latter years of her life in Zurich, where her late husband Charles Banner, the only man she ever loved, had died many years before.