When Madame Preau returns to her own house outside Paris after several years spent in a convalescent home, she immediately notices that the neighborhood has changed. Now, instead of a beautiful garden next door there is a new house. And she can see directly into her new neighbors' windows. Madame Preau quickly feels that something isn't right. Her neighbors have two perfectly healthy children who play in the yard after school. But there is also a third child: a young boy who looks malnourished and abused, and tosses small stones at her window in an apparent call for help. The family denies his existence. But is the little boy real, or merely a hallucination of a lonely, mentally unstable old woman cut off from her own beloved grandson? When the police refuse to listen to her, Madame Preau decides to take matters into her own hands. She's determined to help the little boy, and she'll do anything to make sure he's safe...