When Myriam (Leïla Bekhti) and her husband, Paul (Antoine Reinartz), employ the unflappable and serene Louise (Karin Viard) as the new nanny for their two children, they don’t anticipate how essential she will become to the smooth running of the household. And for her part, Louise embraces her status as honorary family member a little too eagerly. But while Louise is not all she seems, she’s not well written enough as a character to register as anything more than a string of button-pushing plot devices.

This is crass and exploitative stuff that feels too contrived – despite the child peril, lingering shots of knives and the increasingly demented behaviour of Louise – to build much in the way of real tension. Viard does her best, but the credibility of the picture, as well as that of her character, is undermined somewhat by her frenzied attack against an imaginary octopus.