Two young girls are kidnapped by their father after he has murdered their mother, and one car crash later he is hiding them in a cabin in the woods. Just as he is about to murder them too, the father is taken away by an angry apparition, never to be seen again. Five years later, and the father's brother (Game Of Thrones' Nickolaj Coster-Waldau) still hasn't given up on the search for his sibling and nieces. His wife (Jessica Chastain) supports his search, but is also selfishly caught up in her own career. One day, the two girls are discovered in the woods, both feral to the point of barely human, and the law puts them into the custody of their uncle and his wife. But the girls have brought that protective spirit to their new home, too...
Despite the producing presence of Guillermo Del Toro, Mama never quite takes off in the way that it should. When they're discovered, the two young girls are quite unnerving, running around on all fours with frightening speed. But this is soon replaced by the presence of moths, bleeding walls, and the Mama ghost herself. In glimpses, the Mama ghost is terrifying, but when revealed in full, she loses a lot of her horror. The plot is bare and very by-the-numbers, complete with a man of science who doesn't quite believe what he's seeing, so he goes looking for more evidence… in a haunted cabin… in the woods… at night… alone. Yeah, you'll be shouting at the screen during some of the characters' more stupid moments.
Following in the footsteps of the likes of Halle Berry (Gothika) and Hilary Swank (The Reaping), Chastain is another award-winning actress appearing in a below-her-abilities horror movie. As a woman with no maternal instinct suddenly required to become Sarah Connor or Ellen Ripley, she does give good conviction during the more dramatic moments, but doesn't ring true as a scream queen when the time calls for it.
All in all, Mama is a decent enough horror with some good BOO-JUMP scares, but it's not going to have you sleeping with the lights on.