The film is the true story of Marthe Cnockhaert McKenna, a Belgian nurse, played my Madeleine Carroll. She becomes a spy during WW I and easily infiltrates the German high command to pass vital information to the Allied Forces. When she is caught and faced with the firing squad, co-spy
Marshall steps forward and reveals his identity. He takes her place before the firing squad and, soon after, the Allies arrive to save her. Above average performances by Carroll, Veidt, and Marshall save this one from sinking into sticky melodrama.