IN THE FEARSOMELY effective Aussie horror movie "The Babadook," a mother driven round the bend by her 7-year-old goes off.

Most horror movies are pitched to teens, but this one seems aimed squarely at parents, who will squirm when the woman, at her wits end and a little beyond, tells her needy, clingy child she's thinking of bashing his head against a brick.

Uh, mom, you're not supposed to say that out loud.

There are, to say the least, extenuating circumstances. The first thing the movie tells you is that Amelia (Essie Davis) lost her husband in a car accident the day her son, Samuel (Noah Wiseman), was born.

She's pushed her grief aside to care for her morbid little boy, whose fixation with his father's grisly death has turned to a morbid fascination with monsters and magic. Looked at another way, Amelia has channeled her grief into a martyr's determination to meet her child's growing list of challenges.

In any event, she's a single mom, getting more solitary all the time - Samuel's strange behavior keeps him out of school, and keeps Amelia home with him and away from work. When Samuel has a spat with his cousin, poor Amelia even loses the confidence and company of her sister.

She's utterly alone when she picks up a bedtime storybook called The Babadook, and is a few pages into reading it to her son when the story's monster-under-the-bed narrative turns from something Roald Dahl-ish to something almost physically threatening, something alive in her hand, in her house.

She slams it shut, defaces it, burns it, but, as we see, once opened there is no closing The Babadook (an anagram for A Bad Book).

That the book appears just as Amelia is going over the psychological edge is surely no coincidence. We're encouraged to view the monster in her house as her - her unacknowledged guilt at the resentment she feels at having to devote all of her flagging energy/sanity to her child.

No one likes to think there are limits to a parent's love, especially a mother's - tricky but fertile territory for horror, explored here by first time (!) writer-director Jennifer Kent.

She does so with a veteran's skill, confidence, efficiency and artfulness. Note the way she surrounds Amelia, in early scenes, with images of the lonely disconnected woman she fears she may become.

Also exceptional: the movie's design. The book's macabre figures leak into the "real" world as coats and hats and skeleton arms and ghostly faces that hide in shadowy corners.

As the movie builds to a potentially disturbing and perhaps gruesome resolution, we wonder if Kent can find a way to wrap things up that won't make you regret watching it.

This she does. The final moments have surprising emotional heft - affirming of family bonds, but well short of reassuring.