If the ambition is to provide two hours of instantly forgettable, popcorn-munching escapism, it succeeds.

A lot of perfectly good film show their cards early, establish a unique premise and let the audience explore a topic at a leisurely pace, without much in terms of surprise. this film is not one of those films.

This is a must-see and one of the best documentaries - and films - of this year.

The film never slows down or bores, plunging from one harrowing sequence to the next.