When the Germans invade Czechoslovakia, a scientist (James Harcourt) flees to England, but his daughter Anna (Margaret Lockwood) is arrested. She escapes from a camp with the aid of a fellow prisoner (Paul Henreid), but the Gestapo follows and manages to capture her and her father. British Secret Service Agent Dickie Randall (Rex Harrison) heads after them, disguised as a senior German Army officer.
Margaret Lockwood as Anna Bomasch
Rex Harrison as Dickie Randall
Paul Henreid as Karl Marsen
James Harcourt as Axel Bomasch
and returning to the screen after their initial appearance
in Hitchcock'a 1938 film "The Lady Vanishes":
Basil Radford as Charters
Naunton Wayne as Caldicott