I'm not a horror fan, but I quite liked this movie.

Rating: Null/10 (2 June 2013)

There is a 2008 film short, only 3 minutes long, of the same name, 'Mama'. It inspired this movie after del Toro saw it and bargained with the author for a script for the feature-length version. The short film is included as an "extra" on the DVD, it too is an interesting watch.
This movie has a rather simple premise but details are introduced gradually so as to build the suspense. We see an early scene with a father and his two young children driving perhaps too fast on a remote road while it is snowing, and distracted by the older daughter saying "Please slow down daddy" they slid and crashed down an embankment. They find a creepy-looking cabin in the forest and seek shelter there.
The story then switches to five years later, and the man's brother is still spending most of his spare time and spare money looking for the missing man and his daughters. The man and his brother, perhaps twins, are both played by Nikolaj Coaster-Waldau as Lucas (the alive brother) and Jeffrey (who disappeared 5 years earlier). The nominal star of the movie is Jessica Chastain as Annabel, a 30-something who acts more like a teenager and playing bass guitar in a rock band, but married to Lucas. She certainly is not prepared to be a mother.
Let's just say the girls are found but their dad isn't, and Lucas and Annabel are pressed into service trying to re-normalize these two girls, 8 and 6, who have been in the wild for 5 years. Not much goes as planned! The two girls are played by Megan Charpentier as 8-yr-old Victoria and French Canadian Isabelle Nélisse, who spoke no English before being cast, as 6-yr-old Lilly.
Most horror movies I have seen, not a favorite genre of mine, are more boring than horrific. But this one genuinely gave me chills several times, I found it very effective and good entertainment.
SPOILERS: The story goes way back to the 1800s when a woman escaped from a mental ward with a tiny baby, ultimately hunted by a mob. She jumped off a cliff towards water below, but she hit a large branch sticking out, breaking most of her body parts, and she floated dead in the water. But the baby in its wrappings was snagged by the branch and recovered. The dead woman's ghost became the 'Mama' of this movie, she forever haunted one place or the other looking to replace her lost baby. She actually watched over the two girls during that 5-year period. But now she had followed them to their new house, almost killed Lucas, spooked Annabel, and overall was a constant source of havoc in their lives. So they were able to get rid of her only after reuniting her with the remains of her baby, long stored in a box in a government building. But she also took Lilly with her, as Victoria stayed with her new parents, her aunt and uncle.