Alias Mr. Twilight (1946)

Geoffrey Holden is an elderly conman who is a lovable old man when providing his beloved granddaughter with the simple luxuries of life, yet has no qualms when working a racket devised to relieve his victims of their property. Trudy Marshall is the governess of the granddaughter, and is in love with a detective who is about to expose the old man's unsuspected activities.