Schoolgirl Mélanie aspires to a musical career, but during her Conservatory audition, one of the judges, celebrated concert pianist Ariane Fouchécourt, unwittingly distracts her, ruining her chances of a place. Asa result, Mélanie gives up music altogether. Ten years later, Mélanie is working as a law clerk when the company director-Jean Fouchécourt, Ariane's husband-needs a nanny to look after their son. So Mélanie moves into the home of the woman who thwarted her musical career, but what sinister plans does she really harbour?