After the Germans march into Prague, Czechoslovakia, armor-plating inventor Dr. Axel Bomasch (James Harcourt) flees to England. His daughter Anna (Margaret Lockwood) escapes from arrest to join him, but the Gestapo manages to kidnap them both back to Berlin. As war looms, British Secret Service Agent Dickie Randall (Sir Rex Harrison) follows, disguised as a senior German Army officer. His ploy is the not unpleasant one of pretending to woo Anna to the German cause.