This is an intriguing view into the mind of a child dealing with the real-world problem of a mother's rapid descent into mental illness. Though the story is occasionally heart-rending, director Noémie Lvovsky uses nine-year-old Matilde's mix of imagination and make-believe to keep as light a tone as practical while not avoiding the difficulties of the situation. It's set in a different time and social milieu than Rebecca Miller's "Angela", and issues of abuse and religious indoctrination don't drag the tale into a deep pit of despair. Still, Mathilde's situation -- often fending for herself -- will keep you watching in a constant state of anxiety.
All the technical elements are fine. As for the acting, Lvovky's performance as Mathilde's mother will have you genuinely concerned that she's in the darkest stages of depression. Lead actress Luce Rodriguez is also very believable. And the scenarios in which Mathilde finds herself, and the actions she takes, stay close enough to our preconceptions of what a child her age might do that we believe it's real.
The ending, necessitated by Rodriguez's health concerns, is somewhat abrupt, but handled well. And it leaves us with hope. Here is a film well worth watching.