Paula, 40, is nearing the end of her maternity leave. She has to return to work in a few days. But she's not ready. Orso, her youngest, has exhausted her, not to mention her two older children.

With her husband Jérôme, she recruits Tess, an au pair... Tess seems perfect. She's a rare gem. But Paula quickly feels uncomfortable with the young girl. Yet she's the only one. Everyone adores Tess... But she notices changes in her home and the increasing number of incidents that make her seem like a bad mother... She senses something is wrong, but no one believes her when she says Tess wants to harm them... She's told it's probably her baby blues that's making her paranoid. Or does Paula herself have things to hide?

As for Tess, she didn't end up there by chance. What is she looking for when she enters this home?

When a stranger invades your privacy, you have to weigh the risks and consequences. A family is often tiring and exhausting, yet it's when you risk losing it that you realise its full importance.