Trouble coming down the mountain ... Force Majeure. Photograph: Cannes film festival  An unavoidable catastrophe boils within Tomas (Johannes Kuhnke), who -faced with an avalanche while on a skiing holiday with his family -elects to leave them, grab his iPhone and scarper for safety.  Panic sets in before it's revealed that the avalanche is controlled,the wall of snow a harmless fog, and Tomas returns to his broodforever compromised. They've been betrayed, but so has he - his basicinstincts have made a mockery of him.  Swedish director Ruben Östlund's last film, Play, presented a bleak,Darwin-esque analysis of high school bullying. In that film a group ofnorth African immigrant teens bullied their white classmates. Theadults who witnessed the bullying were too afraid to intervene, forfear of appearing racist. Force Majeure also plays with our obsessionwith being seen to do the right thing. Tomas's responsibilities as a dad should trump his own selfish instinct, but they don't. His disgusted wife, Ebba (Lisa Loven Kongsli), could accept that if Tomas could admit his natural cowardice. But he can't. So he keeps on trying to be proper, while his nature marches the other way. It's a force that can't be stopped. An avalanche that threatens to swamp him, for real this time.  Östlund's handling of the avalanche scene is glorious, but it's the centrepiece of a film that is expertly shot throughout. The cinematography, by Fredrik Wenzel and Fred Arne Wergeland, beautifully captures the alien nature of a ski slope - a playground for the affluent classes penned out in the wilds. Imperfections are smoothed out overnight, but the risk of collapse is ever-present. You can see the same in Tomas - the veneer of a handsome, rich family man hides a scared and selfish kid.  It's only when Östlund starts to pull his punches that the slow-roll terror of the film comes to a stop. The director heads off the slopes into Lars von Trier territory - drawing out dark comedy from a pair of friends' role as unwitting jury to Tomas's crime. Although Kristofer Hivju puts in a boisterous performance as Tomas's confidante and protector ("You were probably thinking you should be safe so you could come back and dig them out, right Tomas?") the comic relief feels false set against so much stark humanity.  Östlund invites us to look at ourselves honestly. He points out our inconsistencies, attempts to holdus to account for our worst hypocrisies. Force Majeure is a frightening film. It brushes off our surface layer, shows us the icy truth underneath.  "We survived an avalanche and we were both very frightened," Ebba tells Tomas as they try and rationalise a situation that has no happy resolution. Their kids (brilliant little performances from Clara and Vincent Wettergren) sit side stage as their dad continues to make the story about him. None of them realise Tomas's avalanche has them still. Östlund's sickest joke yet.
Henry Barnes: Ruben Östlund's film, about a father who abandons his family during an avalanche, brushes off the surface layer of human behaviour revealing ice underneath