Paula's psychiatrist suggests that she is suffering from postpartum depression and that she should take a leave of absence,. Paula discovers that the nanny they were supposed to interview just before Tess has been assaulted, and her suspicions only grow. Jérôme doesn't share her doubts and the couple are torn apart, rekindling older rifts.

Having come to the end of her maternity leave, Paula prepares to return to a demanding job at a start-up company. She and her husband Jérôme decide to hire an au pair and recruit Tess, a polished and personable young woman, who gets on wonderfully with the baby and their two teenagers. But Paula experiences increasing feelings of unease as strange domestic incidents start to multiply, casting her in the light of a bad mother.