The Hour Before The Dawn.

Jim is headmaster at a school and has fallen in love with a young Austrian woman, Dora Bruckman, who works for his sister-in-law, May. She meets regularly with her supervisors in London, Mrs. Müller and Kurt van der Breughel, who are posing as Austrian refugees. Dora is ordered to provide German bombers with a bearing to a camouflaged airfield using the headlights of May's car. She is caught in the act by May's son Tommy, but claims May must have left the lights on. Jim and Dora marry to save her from being removed from the district