Two little girls disappeared into the woods the day that their parents were killed. When they are rescued years later and begin a new life, they find that someone or something wants them returned.

Odd set-up gives birth to solid scares.

There are lots of shocks but no real surprises in Andres Muschietti’s Mama, a grimy, unpleasant Canadian-Spanish co-production from the stable of Guillermo del Toro. Based on a slick, atmospheric 2008 short that wowed festival crowds, the padding needed to fill out the concept to feature length is all too evident; surely there are only so many bumps in the night before one flees screaming from the banshee in the closet, right?

the film lives or dies on its ability to frighten and it achieves that with admirable skill

The scariest thing about Mama’s pre-credit prologue is just how much illogic is employed to establish its premise. Due to GFC-related stress, a yuppie dad (Nikolaj Coster-Waldau) kills his co-workers and young wife (all off-screen) before fleeing with his two young daughters into the winter wilderness. Later crashing his car on a snowy embankment, he sets off with the girls into the woods where he finds a deserted cabin. Just as he is about to take all their lives, an 'entity’ saves the girls and, over the next five years, raises them as its own. Read that again: the police dragnet for a multiple-murderer/kidnapper could not find a car off a major road, nor discover a cabin that was so close to the crashed car, two toddlers managed to walked to it in the snow? Or that said cabin went undisturbed for five years, as the girls grew into feral types who walked on all fours? Even by Hollywood standards, it is a ludicrous set-up.

When discovered, the girl’s uncle (Coster-Waldau, again) and his rock chick live-in lover Annabel (Jessica Chastain, unconvincing as as a tattooed goth) take on parenting duties after cinema’s fastest custody hearing. Soon after the new family unit settles into a posh suburban mansion, supplied by shady Dr. Dreyfuss (a hammy Daniel Kash), walls start oozing black goo, moths begin to swarm and a growling, vaguely-female voice begins to emanate from the girl’s bedroom. What then develops is a maternal tug-of-war between Annabel and the spindly-armed ghoul from beyond.

The cabin in the woods is called Helvetia, an alternate term for the Nordic cultures, and the dirt-stained poltergeist that manifests may be a nod to the wood-nymph legends of the region, but it’s never made entirely clear. When the entity is afforded a back-story, it’s of the hoary old 'revenge for mental institution abuse’ kind, so it feels appropriately half-baked.

As expected, the film lives or dies on its ability to frighten and it achieves that with admirable skill (hence the three stars, as there is little else to recommend). Early glimpses of 'Mama’ are fleeting and terrifying; her first full reveal is a genuinely chilling moment. When she unleashes her fury, her arched backbone, glowing eyes and proficiency at scurrying on all fours is suitably unsettling. Megan Charpentier and Isabelle Nelisse, the fine young actresses who play the daughters, didn’t have to witness too much of the horror that makes it onscreen, as Mama is predominantly CGI-created (though entirely convincing most of the time).