Strange Portrait (1966)

Jeffrey Hunter stars as an American expatriate and petty thief living in Hong Kong. He breaks into a mansion one night and discovers an elderly, rich, and insane Chinese woman who talks to a portrait every night. The portrait bears a striking resemblance to the thief, and so he worms his way into her confidence in hopes of stealing diamonds he believes may be in the house. She believes him to be her husband. Eventually he convinces her to open her safe and inside he finds trays of diamonds, and the mummified body of the woman's husband. Suddenly, she slams the safe door shut, trapping him inside. She collapses and dies, leaving him inside the safe forever.