The Power of the Dog: A five-star 'brooding melodrama'

It's been 28 years since the release of Jane Campion's Palme d'Or- and Oscar-winning masterpiece, The Piano, but you can hear its echoes ringing through her new film, The Power of the Dog. Again, Campion has made an atmospheric period drama shot in the wilds of New Zealand. Again, it features a cruel man, a sensitive man, and a single mother who marries one of them. You can probably guess which instrument the single mother plays. But for all its similarities to Campion's best-known work, The Power of the Dog is darker, stranger, and horribly gripping in its own right. Unless you've read the novel by Thomas Savage from which it's adapted, it's impossible to guess where it's going. It also boasts one of Benedict Cumberbatch's most remarkable transformations. Perhaps he told his agent that he was sick and tired of playing socially awkward scientists, and that he wanted to try the most different role imaginable – preferably while wearing a ten-gallon hat.

Cumberbatch stars as Phil, a cowboy who runs a successful cattle ranch with his brother George (Jesse Plemons) in 1925 Montana. The brothers share a bedroom, but they could be from distant planets. Phil is the image of an old-fashioned rancher, an ornery alpha-male who clumps around in his boots and stirrups, despises the idea of anything as namby-pamby as having a bath, and addresses his younger sibling as "Fatso". He is only happy when he is crossing the plains on horseback – and he's usually not happy even then. George, meanwhile, is a well-scrubbed, smartly dressed, mild-mannered fellow – and much to Phil's frustration, he refuses to rise to any of his brother's insults.

Cumberbatch paints a finely detailed portrait of a thoroughly objectionable man, pouring Phil's anger and resentment into every glare, every twisted grin, every mocking word, every suck of his hand-rolled cheroot. He can even be belligerent when he plucks a banjo string – and if that's not worth an Oscar nomination, I don't know what is. What Cumberbatch's riveting performance doesn't reveal, though, is the source of Phil's bile. Why does he keep pushing and prodding George? Why can't he enjoy being so skilled at his work and so adored by his ranch hands? How has he been damaged? What, in short, is this guy's problem?

It feels as if the simmering loathing could boil over into violence at any moment. But Campion, who wrote as well as directed, keeps us guessing

Whatever the answer to these unsettling questions, Phil's issues are exacerbated when George announces that he has married Rose (Kirsten Dunst), the timid, widowed owner of a nearby hotel. Not only will she be moving into the family home, but her son Peter (Kodi Smit-McPhee) will be staying, too, during his holidays from college. And if George falls short of Phil's picture of how a rancher should behave, the skinny, effete, artistic Peter is far worse. The last time a cowboy was this upset about an interloper in his house, it was Woody in Toy Story when Buzz Lightyear moved in.

It feels as if the simmering loathing could boil over into violence at any moment. But Campion, who wrote as well as directed, keeps us guessing. Like Rose, we're permanently on edge, trapped in a dark, drafty mansion where we are always being watched by either a venomous brother-in-law or a stuffed-and-mounted animal head. Rather than hurrying along the plot, Campion immerses the viewer in a world that seems creepy to the point of being supernatural, but also completely real. Much of the film is shot in natural light, with plenty of sensual close-ups of sweat and grime. Although it was made in New Zealand, you could believe that its Wild West buildings had been standing on the bare Montana landscape for years. The actors' horse-riding, rope-splicing and, yes, bull-castrating techniques appear so effortless that their training must have taken weeks of effort. And the characters have the quirky habits and hobbies of real people rather than Western stereotypes: just when you think you know them, you're surprised by a scholarly reference to ancient Rome, a brief appearance of some doll's house furniture, or a sudden furious bout of hula-hooping.

What's unique about The Power of the Dog is that it seems at first to be an epic Western, but it becomes a brooding gothic melodrama in which relationships shift and long-buried secrets surface. Its slow-burning psychological mysteries may frustrate some viewers. But others will be gripped by the way Campion twists the conventions of the American frontier drama: the fact that its jittery score is by Jonny Greenwood isn't the only thing it has in common with There Will Be Blood.

It's a film which shimmers with intelligence, and if the plot isn't clear until the very last scene, well, it's worth the wait. When that scene arrives, the purpose of every previous scene snaps into sharp focus, leaving you with the urge to go back to the beginning and watch the whole thing again.