In 1968, Sue and David's Dad, an architect and developer, has bought an old, and very large, house outside Stockport, which he wants to knock down to make way for a new housing estate. In the meantime the family have moved in. They discover that two young sisters disappeared from the house shortly after the second world war. They also learn that their Dad bought the house from the mother of the lost girls. They realise that once the house has been demolished, and the site developed by their father, that all trace of the missing girls will be lost forever. They resolve to solve the mystery of the girls' disappearance, using an old book that they have found left behind in the house. They start to follow in the footsteps of the lost girls. Their decision and discovery of the facts about the lost sisters, affects their lives forever.