Calling Scotland Yard: The Missing Passenger (1954)

Two sisters become recluses after being jilted by a man who was courting both. He couldn't make up his mind so he just moved to South America for a few years. When he returns for a visit, one of the sisters imprisons him a room in their house, where he remains as a prisoner for many years. After one sisters dies, the other becomes so weak that she allows the man to escape, and the shock of seeing him come from the room frightens her to death.