Damien lives with his mother Marianne, a doctor, while his father, a pilot, is on a tour of duty abroad with the French military. At school, Damien is bullied by Thomas, who lives in the farming community up in the mountains. The boys find themselves living together when Marianne invites Thomas to come and stay with them while his mother is ill in hospital. Damien must learn to live with the boy who terrorized him.

Being 17 rides the roiling emotions of adolescence through a coming-of-age melodrama whose narrative turbulence smartly reflects the confusion of its protagonists.