The Secret Life of Walter Mitty (1947)

In New York the clumsy Walter Mitty is the publisher of pulp fiction at the Pierce Publishing house owned by Bruce Pierce. He lives with his overbearing mother and neither his fiancée Gertrude Griswold and her mother nor his best friend Tubby Wadsworth respects him. Walter is an escapist and daydreams into a world of fantasy many times along the day. When Walter is commuting, he stumbles in the train with the gorgeous Rosalind van Hoorn who uses Walter to escape from her pursuer. Walter unintentionally gets involved with a dangerous ring of spies that are seeking a black book with notes about a hidden treasure.