In a wrecked post-war Berlin, a congressional committee from the United States of America comes to the occupied city to investigate the moral of the American troops. The conservative republican Congresswoman Phoebe Frost from Iowa brings a birthday cake to Captain John Pringle from his girlfriend also from Iowa. Later she splits from the other congressmen and decides to investigate the decadence of the military on her own, and not in accordance with the official speech and visit promoted by Colonel Rufus J. Plummer. She meets two American privates that believe she is German. They take her to the night-club Lorelei, where the lead attraction is the singer Erika Von Schluetow, who is the secret mistress of Captain Pringle. Congresswoman Frost overhears that Erika belonged to the Nazi Party and is protected by a senior officer, and she enlists her fellow countryman Captain Pringle to help her in the investigation of Erika. The officer seduces Frost to protect Erika and himself from martial court, but the jealous former lover of Erika, the Nazi Hans Otto Birgel, is seeking revenge against his competitor.