1933. It is the fourth year of the Great Depression. For John Dillinger, Alvin Karpis and Baby Face Nelson, it is the golden age of bank robbery. After serving a ten-year prison sentence, John Dillinger embarks on a cross-country bank-robbing spree with help from his associates: faithful driver Red Hamilton, cocky lookout Homer Van Meter, and murderous hothead Baby Face Nelson. He relocates to Chicago, where he meets hatcheck girl Billie Frechette and falls in love, but struggles to reconcile his new romance with his life on the run. Meanwhile, FBI director J. Edgar Hoover has enlisted Special Agent Melvin Purvis to use the latest techniques and equipment to catch Dillinger-Public Enemy Number One-even as Purvis realizes that doing so may stretch his principles to the breaking point.