The ridin', ropin' and shootin' Billie (Käthe von Nagy) is shipped from the Argentinian pampas to Europe to be polished girls' boarding school. Cheerfully untamable, she constantly violates the rules of the boarding school and is thrown out. So she gathers other girls around her and founds the Republic of the Teenage Girls on a deserted island, and becomes its president herself.
The film tells the story of an ambitious young man, Tom, who loves Grete, daughter of the manager of the national railroads; but Grete's father prefers Lund, an upright and uptight army officer. To prove his worth, Tom organizes a daring robbery of the nightly Bergen Express in the hopes of outwitting his rival, who's been assigned to track down the thieves.