When mother of two children Myriam (Leila Bekhti) decides to go back to work despite her husband's initial reluctancy, the couple starts looking for a nanny. After a very selective process, they finally find the perfect candidate, Louise (Karin Viard), a poised 40-year old woman who is an instant hit with everyone. But as Louise makes herself indispensable to the family, she starts revealing her unsettling true self.