Tells a fascinating and unsettling true story, and does so well, without pretending to have all the answers.

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

I think this is a new genre that they're all sort of working their way through it and haven't got all the kinks worked out yet but it's a genre that works for me.

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