An empty car sits abandoned in front of a big house in an affluent suburb. A report of a shooting at an investment firm blares on the radio; we gather it is the height of the 2008 financial crisis. Jeffrey (Nikolaj Coster-Waldau), dazed and covered in blood, shoots his ex-wife, grabs his two young daughters and drives off into the mountains. Stumbling through the woods, he happens upon an abandoned cabin. His older daughter sees movement inside. He builds a fire, and prepares to kill his daughters and himself. Before he can go through with it, he is grabbed by...something. So begins Mama, a ghost story more interested in atmosphere than cheap thrills.
Five years later, Jeffrey's twin brother Lucas (also Coster-Waldau) hasn't given up hope of finding his nieces. A map of the countryside covers his wall, and he pays groups to search the forest. Just as the money runs out, the cabin is discovered, and both young Victoria (Megan Charpentier) and Lilly (Isabelle Nelisse) are still alive, though five years in the woods has made them feral. They speak of a presence they call Mama, but psychologist Dr. Dreyfuss (Daniel Kash) believes Mama to be an imaginary friend conjured by the girls' damaged psyches. After a few months of observation, Lucas is awarded custody, and he brings the children home to his girlfriend, the loving but reluctant Annabel (Jessica Chastain in full punk rock mode.) It becomes obvious to anyone who has seen a horror film that something followed the girls home.
An "accident" sidelines Lucas early, leaving the girls with Annabel as Lucas recuperates in the hospital. The performances of the young actresses are extraordinary, as both Victoria and Lilly slowly begin to warm to Annabel. Chastain proves again her versatility as an actress. The first time we see Annabel she is a rocker chick rejoicing at a negative pregnancy test; by the end she discovers maternal instincts she never knew she had. Her charisma and sympathetic performance make up for one of the inherent flaws of the movie, one it shares with most films in the genre: the characters' inability to sense imminent danger before it is too late. People in horror movies have never in their lives seen a horror movie. Even the psychologist, who figures out earlier than the others what is going on, still insists on going to the cabin alone and at night!
Director Andres Muschietti doesn't spare the gotcha moments. They come early and often, but he shows restraint in not fully revealing Mama until the climax. He does a good job of building the tension; the best moments come when we see something that Annabel does not. And when we see the Big Bad, she is a doozy. Embodied by actor Javier Botet and an abundance of CGI, Mama is one scary creature . There is of course a back story for the ghost, and in making her just a bit sympathetic, the filmmakers elevate Mama above the malevolent forces in movies like The Possession and Paranormal Activity. The climax is unexpected and poignant, which makes Mama just a bit better than the average horror movie.