They want to be the perfect couple, balancing children and career, trying to do everything right. And they find the ideal nanny who makes all of this possible. But how well can you really know a stranger? And how much can you trust them? Myriam and Paul feel lucky when they hire Louise—a nanny straight out of a storybook who takes care of their two small children in their beautiful Parisian apartment in the 10th arrondissement. They have no idea of the depths and vulnerabilities of the woman to whom they entrust their most precious ones, or of the deep loneliness that threatens to engulf Louise. Until one day, tragedy strikes the small family, as unstoppable as it is horrific.