The easy synopsis might go thus: Leonardo DiCaprio’s expert tracker and marksman, Hugh Glass, is mauled by a bear and left for dead by his comrades, not least the treacherous, flea-bitten John Fitzgerald (an almost unrecognisable Tom Hardy). Hauling himself across the icy north-western wilderness, Glass miraculously survives his injuries and resolves to find the man who left him behind. Iñárritu, who shot Birdman in what looked like a single flowing take, pulls off a different yet similarly mesmerising technical feat here. His handheld camera swirls and glides across the rapids, snow and earthy forests, yet also gets in close to study his characters. A battle sequence near The Revenant’s opening has a startling immediacy, the lens whipping back and forth as a camp full of trappers is shot full of arrows. At one point, Iñárritu stages a kind of relay race of violence: a hand-to-hand fight flows seamlessly to a warrior on horseback, who in turn is shot by a marksman, who in turn is hit by a flying axe. Once that sequence is over, Emmanuel Lubezki’s crystal-clear digital cinematography has become all-enveloping. DiCaprio simply is a bearded, 19th century man clinging to survival. Hardy really is a scarred, faintly sociopathic mercenary with designs on buying some land down south. The filmmakers’ cameras are simply there, recording the action. In Birdman or Amores Perros, Iñárritu’s directorial flourishes occasionally drew attention to themselves; here, they’re so perfectly of a piece with the Cormac McCarthy-esque storytelling that it’s only as the final credits roll that its brilliance springs to mind. It’s a world of violence, cruelty and above all separation; rival groups of people killing and being killed, attacking and counter-attacking. Murder follows murder, revenge follows revenge. In the final analysis, even Fitzgerald’s betrayal makes sense from a certain standpoint; in a brutal world, split-second decisions can have far-reaching consequences. The Revenant depicts it all not so much as a horror but a tragic inevitability. We can only guess at what the actors and filmmakers went through to capture such an authentic-looking movie. Taken at face value, DiCaprio’s ordeal looks positively harrowing; within the first hour alone he’s eaten the marrow from the bones of a mouldering bear carcass, bitten the head off an apparently live fish, and chowed down on the steaming liver of a fallen buffalo. There’s more to DiCaprio’s contribution to the film than stunt eating, however; it’s also a captivating physical performance, his face conveying horror, determination and despair in roughly equal parts. The supporting cast is also worth a mention: Domhnall Gleeson as a lily-livered captain; Will Poulter as a young tracker cowed into leaving Glass behind by the imposing Fitzgerald. The icy chill that pulses through The Revenant is difficult to shake. It’s a long, brutal, sometimes difficult to watch film, but it’s also an unforgettable one. The Revenant is out in UK cinemas on the 15th January.