The prologue shows a distraught father, apparently devastated after a financial setback, driving his tiny daughters up snowy mountain roads to a vacant small summer house in the woods. Just as he is about to shoot the older girl, the man is prevented from doing so by some kind of beast which is vaguely glimpsed by the youngster but not clearly.
Five years later, Victoria (Megan Carpenter) and Lilly (Isabelle Nelisse) are discovered; miraculously, they have somehow survived by themselves, although they look like feral beasts, hopping around on all fours and the little one, especially, scarcely seeming human.
Taking them in, despite highly dubious qualifications to care for such demanding cases, are the dead father's handsome artist brother Lucas (Nikolaj Coster-Waldau) and his punky grrrl band girlfriend Annabel (Jessica Chastain, sporting tats and a haircut that's somewhere between Joan Jett and Liza Minnelli).
Living in a loft in clearly tenuous financial circumstances, the couple are set up in a surpassingly luxurious suburban home by a prominent doctor, Gerald Dreyfuss (Daniel Kash), for the exclusive right to study the girls and, presumably, help them fill in what they've developmentally missed through their human deprivation.
Victoria, a bright child who had learned how to speak well before her father's freak-out, isn't such a problem. But Lilly remains more animal, or even insect, than human, scurrying around like a spider in her own little universe.
And, clearly, they are not alone. Weird apparitions materialize: Large moths and web-like patterns on the walls and, in a brilliantly architectural fixed shot from a hallway, the sight of little Lilly tugging playfully with an mostly unseen presence through a door frame. This may be a pristine, immaculate looking house, but it's also haunted.
With a couple of obviously expendable supporting characters hanging around just so they can be dispatched by frisky culprit lurking in the walls, Muschietti does a pretty good job of sustaining one's interest until finally needing to let the cat (or whatever it is) out of the bag.
The director cheapens his work by overly relying upon loud and abrupt musical cues to unsettle the viewer, but the enterprise otherwise sports a classy profile thanks to Antonio Riestra's refined cinematography, Michele Conroy's expert editing and generally top production values.
“Mama,” which runs one hour, 40 minutes, is rated PG-13 for violence and terror, some disturbing images and thematic elements.