Who — or, rather, what — is the Babadook? And why is it that, once you let the Babadook in, you can never get rid of it?

First and foremost, The Babadook is an Australian horror film by writer-director Jennifer Kent, a former actor who apprenticed with Danish filmmaker Lars von Trier during the making of his 2003 film Dogville before going on to make her own short film, Monster, upon which The Babadook is based.

The story, which draws on Victorian horror themes of domestic strife and loss of identity as well as from classic scary movies like Let the Right One In and Rosemary’s Baby, is fairy-tale simple: A struggling single mother, Amelia (the excellent Essie Davis), is losing her grip on life. Seven years ago, her husband was killed while driving her to the hospital while she was in labor. Her son, Samuel (Noah Wiseman), is a precocious but impulsive child with a wild, sometimes violent imagination. As Amelia struggles to make ends meet at her hospice job, Samuel’s isolation and unruly behavior further isolate him, turning him into a “problem child” at school.

One night, Samuel grabs a previously unnoticed book from the shelf for his bedtime reading. As Amelia reads from Mister Babadook, a sinister threat takes hold of mother and child: The pop-up storybook, about an insidious shadow creature who stalks the darkness, seems to immediately insinuate itself into the fabric of their lonely lives. The Babadook seeks a kind of murderous spiritual possession, a flowering of darkness like some evil Id, as it warns, “The more you deny, the stronger I get.”

With The Babadook, Kent has created a smart, rich, layered horror film that is at once genuinely spooky and emotionally resonant. She taps a primal vein of parental anxiety — can I protect my child? And, worse, can I protect my child against my own darkest impulses? — and then brilliantly literalizes that fear, turning a kid’s fable about a demonic presence into a meditation on self, shame and the way the suppression of our deepest nature can turn us into monsters.

As a besieged mother paralyzed by grief and slipping into insanity, Davis is a marvel; her transformation channels Jack Nicholson’s plunge into madness in The Shining — though, unlike Nicholson’s comically gruesome Jack Torrence, Amelia remains a sympathetic figure, a symbol of motherhood imperiled. Wiseman is a fine young actor whose portrayal of the fierce confusion of childhood is terrifying and heartbreaking.

More and more these days, horror films have become the domain of objectified violence and funhouse irony, where regurgitated, unsubtle plots do little more than fulfill expectations of easy titillation that explode in bloody chaos or shatter into sophomoric meditations on good and evil. The Babadook, however, is the antithesis of genre trash. This is a sophisticated and psychologically astute thriller that burrows under the skin, relying less on shock than on atmosphere, until all hell breaks loose. (Bijou Metro)