Jean Arthur stars as Congresswoman Phoebe Frost in Wilder's satire of American sexual mores. She arrives in bombed-out postwar Berlin in 1947 as part of a congressional delegation assigned to investigate the moral behavior of the American occupying troops. As part of her mission, she delivers a cake baked by his fiancee to Capt. John Pringle (John Lund), who immediately trades it on the black market for a mattress, which he takes to the apartment of his current girlfriend, Erika von Schluetow (Marlene Dietrich), an alluring German nightclub singer. While touring the city, researching the G.I.s appetite for blond German women and alcohol, Phoebe, mistaken for a German, is picked up by some of the soldiers and taken to a club which features the singing of Erika. When she sees a familiar cake being served, she becomes suspicious and orders John to watch the woman's apartment to identify her American lover. After seeing some newsreel footage of Erika with Hitler, Phoebe asks John to show her the woman's file, but he distracts her from further investigation by coming on to the congresswoman, who responds with surprising passion. A comedy edged with cruelty, it features one of Dietrich's quintessential performances.