Paul, 12, lives with his mother, a cleaner in a private clinic in the middle of the woods.
In this clinic, Dr Loisel treats rich people afflicted with serious mental illnesses. When he is not helping his mother, Paul runs to the woods to do some birdwatching, his great passion.
One day, Gloria, a schizophrenic 15-year-old, arrives at the clinic. Paul immediately falls in love with her. A clumsy love, a deep friendship is born between the two children. Believing that Gloria is in danger and despite warnings from adults, Paul helps her escape.
During their escape, Gloria pushes the director down the stairs and accidentally kills her. Paul's goal is to drive Gloria to her grandfather's in Brittany since she said that she had never been happier than when she was there.
This is the start of a long drift that will drive the two teenagers to the heart of madness.