London couple Tess and Alfie Palmer can not have their own children. They adopt two girls who are orphans from a Canadian, non-state-recognised placement agency. The mother of the children was murdered two years ago. Four-year-old Grace looks carefree, bright and fun-loving, whereas ten-year-old Heather is more depressed and serious. As time goes on, Heather proves stubborn and even violent. But adoptive mother Tess does not despair, as her training as a child psychologist leads her to believe that Heather appears to have a secret. Therapy talks with a colleague bring no progress, so she decides on a daring venture - a return to the scene of the crime in the hope of getting Heather to talk. She now considers it a possibility that Heather could have murdered her own mother.