Nick Vass’s review published on Letterboxd:
A generic ghost story that mostly manufactures on short, sharp shocks just like the majority of modern horror. These tropes completely succumb the last 40 minutes, otherwise there is some initial promise about depicting the psychologically unsettling effects between two disturbed little girls and how Amanda (Jessica Chastain) is entrusted to take care of them.
Parental guidance is definitely not her strong suit. The eldest Victoria cannot adjust to the real world and occasionally snaps. Lilly lurks in the shadows and crawls like a distorted figure. All of this is some pretty cool feral child stuff, but limited time is spent on showing Amanda's difficult capabilities on how to deal.
Before we know it, "mama" makes her entrance, the piercing sounds jump-scare on predictable cues, and of course Amanda is silly enough to look into places where she shouldn't. Despite the actress being in a horribly miscast role of punk-rock bassist, goth outfit, shedding a half-sleeve and wearing mascara - she gives her best effort and has a believable companionship with Coster-Waldau (yet largely ignored for most of the film.) Certainly not bad and a passable time-killer, but it's unable to capitalize on say... the escalating tension of Insidious or other films of the supernatural.