This heartbreaking film is like a bad dream: there's a sense of bleakness and you can't see anything clearly. Its saddest sections are filmed undercover in the closed world of North Korea where we discover, with a lurching stomach, that it's not uncommon to see people lying dead in the street. Reporter Kim Jung Eun tracks down dissidents who have fled the country and builds a picture of the makeshift underground: a big force for change is smuggled videos of foreign soap operas; one man who managed to paste up a defiant poster and film it has become a hunted hero. It becomes unbearably moving to glimpse the plight of a whole nation through snatches of secretly filmed footage, but by the end you feel the very least we can do is watch.