Juliette, separated from her husband, Pierre brings up his daughter, Julie, on her own. She does not go to school and only lives for the piano, revealing herself to be a virtuoso. The latter then becomes jealous of her own daughter.

Juliette teaches the piano in a small provincial town. She lives alone with her daughter, Julie, a young musician prodigy, which only Juliette, who is also her teacher, knows. Although she passionately loves her daughter, Juliette nonetheless sees daily, through her musical gifts, the reflection of her own limits. Julie is what she herself has always dreamed of being and the image of this perfection, achieved with insolent ease, soon becomes too heavy to carry. A professional musician passing through the city, hearing Julie play one day, thinks it is her mother. Juliette does not deny it, lets lies settle, appropriates the history and the talent of her child. Little by little, she loses control of her thoughts and actions, then changes completely, going so far as to endanger Julie's life.