The Secret Behind the Locked Door

Dinah Meredith takes her much younger brother Tim to play at a nearby ruin of an old manor house. On separate occasions they think they see a mysterious face at one of the windows. Dame Truman, who claims to be the only occupant of the habitable part of the house, lets them move about inside freely. Soon they come upon a locked door. Tim discovers that someone is living behind the door. Dinah and Tim think someone might be kept prisoner there and decide to liberate whoever it is. Before they can do so however, they find the door open...