Chicago, January 1933. Danceland has a big sign, "30 girls, open until 2 a.m." Inside, customers mingle with the dime-a-dance girls. Hoofer Ellie Haskell says goodnight to the owner, Marty Pulaski; outside, she is immediately shot by a sniper on the roof of a building across the street-- the sniper is Herbie Pulaski, Marty's mentally disturbed brother. Lt. Roy Gunther is on the case, he questions Marty, who has 20% of the dancing racket. However, Marty is sure his main competitor, Vince Bogan who owns 80% of the dance racket, is responsible for the killing; Marty phones Bogan and threatens to rub him out.
Back at Ness' office, Lt. Roy Gunther discusses the case with Eliot. Ness has to go to New York to testify before a grand jury, he'll be gone a week-- he puts Lee Hobson in charge. Marty has his brother Herbie drive him over to Bogan's place; inside, Marty shoots Bogan. Outside, when Herbie hears the shots, he reaches for his rifle in the trunk of the car-- and has a flashback to shooting Ellie. Herbie panics and drives off with the getaway car. Lt. Roy Gunther and Lee Hobson question Marty. Meanwhile, another hoofer at the club, Fran, is sweet on Herbie.
At Bogan's funeral, the overlord who was boss to both Bogan and Marty, János "Jake" Szabó, is upset with Marty for the killing. It was Szabó who had divvied up the dancing racket: 80% for Bogan, 20% for Marty. But fast-talking Marty says that Bogan crossed the line by killing the girl; Szabó buys that, for now. Back at the dance club, Fran is talking to Marty; when Herbie sees Fran, he has a flashback to Ellie Haskell. Herbie goes on the roof again with his rifle, but he's surprised by an old housewife who goes to the roof to get her laundry; Herbie shoots her. With this new sniper killing, Szabó knows that Bogan was not responsible for Ellie's death. Szabó gives Marty 24 hours to provide proof that Bogan did it, or else!
Herbie has a nervous breakdown; he tells Marty that Ellie was a nice girl, but Marty made her dirty, and she's better off dead. Next day, Eliot Ness is back in town. Marty needs a scapegoat, so he puts a gun to Cully's head; Cully used to work for Bogan. Marty forces him to write a note: "To the police, in case of my death," and then name Bogan and Szabó and Marty, and outline the setup of their operation. Marty shoots Cully. That night, Marty shows Szabó the note, and says Cully was playing both sides against each other. Szabó buys that, for now. But then Herbie kills Fran, and the headlines read: "Another sniper killing." This time, Marty can't give Szabó any more phony excuses; he decides to offer Herbie to Szabó.
But that doesn't get him off the hook; Szabó says, then you killed my very good friend Bogan for nothing. Back at Ness' office, Eliot gets a report from the sanitarium that Herbie spent 6 month in. Marty drives Herbie to meet Szabó at his aviary; Ness and his men tail them. At the aviary, Marty confronts Szabó; Marty had lied so much, that now, even though he was finally telling the truth, Szabó doesn't believe him. Szabó's enforcer shoots Marty. Just then, Ness, Enrico, Lee Hobson and Lt. Roy Gunther break the door down, and there's a shootout. Szabó and his enforcer were later executed for killing Marty. As for Herbie, he spent 8 years in the northern Illinois State hospital at Elgin; after being released, he led a productive life. (synopsis by: kdh)