Gd ore is boring. So much chainsaw-massacre splatter has been shoveled movie audiences' way, we've become inured.

"Mama" is a smartly refreshing departure, a truly scary movie exemplifying horror at its purest. It elicits sudden, heart-constricting spasms of fear rather than simply trying to gross us out. And it does so with such finely honed style, you could call it "high creep."

The well-shot flashback beginning portends a good story to come. A father (Nikolaj Coster-Waldau) who has just killed his estranged wife speeds into the snowy mountains with his two young daughters. After the car crashes, the three stumble upon a seemingly abandoned cabin, where a malevolent she-ghost having a permanent bad-hair day makes short work of Dad, but takes a motherly shine to the kids.

Spring forward five years. The recently discovered feral girls go to live with their artist uncle (also played by Coster-Waldau) and his rock-bassist girlfriend Annabel (Jessica Chastain, who should get a special award for range this year). The phantom, feeling protective and proprietary toward the girls, slithers along for the ride, and proceeds to wreak ghastly havoc on the newly formed family when she's not skulking in closets or spitting moths out of walls.

Director/ co-writer Andrés Muschietti keeps the goosebumps coming with unanticipated frissons, like the startling way in which the girls spider-crawl on all fours, and the ungodly noises spewing from the stringy, contorted apparition that is Mama.

Her character looks like a special-effects contrivance but is not, entirely. She's played by a male actor (Javier Botet) with a rare condition called Marfan Syndrome, an inherited connective-tissue disorder that elongates limbs and makes fingers look like E.T.'s. Rather than comfort like the beloved alien, though, Mama's bone-thin, stretched-out digits threaten to crush with possessive, obsessive love.

Muschietti frightens not only with superb visual effects and expert pacing, but by accessing the shame and fears we bury deep in our psyches. What parent hasn't, at least once, looked at a screaming, kicking toddler and thought, "This can't be my darling, it's a monster" ? And what mother hasn't felt such intense love for her children, it borders on ferocious?

The film's executive producer, Guillermo del Toro, wrote and directed the troubling, darkly magical "Pan's Labyrinth." His imprint is also apparent on "Mama," which breaks the same unspoken Hollywood rule: Things don't end well for the children, at least not both of them. While that might leave some viewers dissatisfied, it saves the story from a pat, predictable finish.

"Mama" isn't perfect -- a few head-scratcher plot leaps and loose ends annoy -- but it's a relatively sophisticated palate cleanser in an overcrowded, derivative genre, and scary enough that you might shine a flashlight into your air vents before going to sleep.