Fantastic Night (1942)

Denis is distracted: he's studying all day for philosophy exams and working all night at the flower market; plus, whenever he closes his eyes, he dreams of a mysterious woman in white. His girlfriend Nina is annoyed at him for his inattention, so she steps out behind his back with a friend of his. One night, while napping at the flower mart, he pursues the mystery woman in what he thinks is a dream, and finds himself with her in a restaurant with her father and her fiancé, then on to a magic shop, the Louvre, a nightclub, and a mental asylum. During the night, he discovers a plot against her, and still believing it's a dream, goes to great lengths to try to save her.