Half Angel (movie, 1951)

Nurse Nora Gilpin plans are to marry building contractor Tim McCarey and settle down. But one night a sleepwalking Nora slips into a provocative dress and goes to the home of startled lawyer John Raymond, for whom she doesn't care much during the day. She does not reveal her name and he cannot figure out where they have met, but they spend several hours together until she gets away before John notices.