Snowtown (18)

Starring: Lucas Pittaway, Daniel Henshall, Louise Harris

Like the snappy dog in the park that sprints towards you – the one whose owner calls after, "don't worry, he's quite friendly" – Snowtown is a film most people would wish to avoid. And they would have good reason, because it hides a vicious bite. Everything about it says, "I do not want to be your friend". I sat through its two hours in a helpless cringe of premonition.

The bad news, I'm afraid, is that it's also horribly compelling, and very well-directed. Justin Kurzel, making his feature debut, has an intuitive understanding of actors and a feel for tension that Hitchcock would have admired. He and his co-writer Shaun Grant have adapted their screenplay from two books about the Snowtown murders in South Australia during the 1990s, a case also referred to (gulp) as "The Bodies in the Barrels". Yet while you must brace yourself for something warped and harrowing, Snowtown has thoughtfulness on its side; it is as much about the nature of male influence as it is about the deranged psychology of killing. Here, the one feeds off the other.

Set in an impoverished, run-down suburb north of Adelaide, where sunshine appears to be rationed, the film unfolds a subtly horrifying story of neglect and abuse. Lucas Pittaway plays Jamie, a 16-year-old living with his mother Elizabeth (Louise Harris) and two younger brothers. The family is splintered in a way that's never quite clear: Elizabeth's ex (and the boys' father?) is still a sort of friend, with a son of about Jamie's age, but she also seems to be involved with a neighbour across the road who babysits when mum's away. Exactly what this neighbour does in her absence is revealed in a sequence of cuts to Jamie and his brothers photographed in stark poses, nude. It's the first – but by no means the worst – of the nasty shocks the film has in store. (The behaviour of Jamie's elder brother, Troy, for instance, must be seen to be believed). Elizabeth rages against the abuser, impotently, because he's soon out on bail and back in situ.

Enter John (Daniel Henshall), a charismatic stranger with a twinkle in his eye and a weird retinue of friends and hangers-on. John takes the family under his wing, sorting out the paedophile over the road and presiding over a kangaroo court of locals who see vigilante justice as the only sort they can rely on. He forms a particular bond with Jamie, taking him for motorbike rides and giving one another DIY crewcuts. Elizabeth approves of John as a surrogate father, though she fears him too, and by slow degrees we begin to understand why. The first cause for alarm is his goading Jamie to pick up a gun and shoot a dog. If only it had ended there. John, who initially appeared a rough but righteous scourge of child abusers and junkies, is revealed to be far less discriminating in his choice of victims; indeed, he is John Bunting, a name resonant in Australia as the country's most notorious serial killer.

The brooding atmosphere darkens and congeals into something nightmarish as a psychopath's modus operandi is laid bare. The undercurrents of wrongdoing, hinted at by Elizabeth's strangled silences, eventually break out in scenes of brutish violence, soundtracked against a banal background of cricket on TV. Even more upsetting is the sense of Jamie being corrupted by this barbaric brotherhood, and the matter-of-fact spirit in which John selects his prey. Spotting a local kid with mental health problems, he asks: "Think he'll be missed by anyone?"

Vital to the audience's willingness to stick with this squalid stuff are the contrasting performances of murderer and accomplice. Daniel Henshall, as pudgy and affable as a teddy-bear in his early scenes, commands a stillness of gaze that finds its repulsive echo in a scene of a snake approaching its dangled supper (a mouse).

Pittaway, another screen debutant, was discovered by the casting director in a shopping mall, and carries the mood of the film in his fearful, black-eyed gaze. His haunting resemblance to the late Heath Ledger can't help but amplify the sense of tragedy waiting upon Jamie, who in reality is serving a life sentence in an undisclosed prison.

Snowtown digs into the same netherworld of backyard criminality as David Michod's recent Animal Kingdom and Rowan Woods's The Boys, films that present the idea of family togetherness in the bleakest possible light. It also shares that frightening sense of Australia's vastness, its vaulted silver cloudscapes ominously shot by Adam Arkapaw. This is a land all too easy to disappear into – I'm also thinking of Wolf Creek, a wilderness movie so scary you'd never go near a country road again. But where else to go, if one is to escape the constricting miseries of a dead-end dump like Snowtown?

The heartstopping finale, a long journey into night, points up another excellence of the film, Jed Kurzel's insistent, unsettling music. Whether you should go and see it or not depends on your stomach for grisly scenes of rape and torture. Such things are difficult to un-see. A Mozart clarinet concerto or a screening of Singin' in the Rain might be advisable soon afterwards. They may not restore your optimism about the world, but they will offer a useful antidote to the experience of Snowtown, and to the dark places it takes you to.