Plot: a family are celebrating a mother's 70th birthday in a lavish hotel in Korea when suddenly a toxic white fog spreads through the area. The people in the hotel manage to get to the rooftop, a helicopter comes and rescues all but two of them: one of the mother's sons who is a loser into rock climbing, and the deputy manager whom he loved back when they were in a rock climbing club. Together they try to escape by clambering from rooftop to rooftop.

A well-made film, with very human leads in an impossible situation. Their obstacle course is varied and treacherous, but there are moments of triumph and comedy and almost alien beauty. There are formulaic elements here, the hotel manager is a slime ball, but the film is fresh and enjoyable.

On a deeper level one could understand the film commenting on voyeurism - the couple's desperate race for survival thanks to drones becomes filler for news programmes, becomes entertainment and something for the spectators to talk about. Though as viewers we can dismiss this as fiction nonetheless we are voyeurs, to enjoy the film we have to enter into it, willingly suspend our disbelief, and watch safely from our couch of armchair or beanbag.

Great film, great performances.