Spy in Black

The Spy In Black is the story of a German World War I submarine captain (Conrad Veidt) who is given a mission to discover British intelligence secrets. Once he arrives in the Orkney Islands, he meets up with a female schoolteacher (Valerie Hobson), who happens to be a German agent. Veidt falls in love with Hobson before discovering she's actually a double agent for the British. In America, Spy in Black was originally released under the title U-Boat 29.