Idealistic Iowa congresswoman Phoebe Frost (Jean Arthur) touches down in postwar Berlin on a fact-finding mission about legendary cabaret singer Erika von Schlütow (Marlene Dietrich), long rumored to be the former mistress of one or more high-ranking Nazi leaders and now reportedly intimately involved with an unidentified American military officer. Frost falls for her military escort, Captain John Pringle (John Lund), unaware that the handsome American is the singer's secret paramour.