Back in the 1960s, the Indonesian government was overthrown by the military, and the country descended into vicious turmoil. Unable to cover the entire nation in tyranny themselves, the military outsourced its violent wants to local gangsters and paramilitary groups, who went on to form death squads, allowing them to beat, rape and murder anyone they suspected of being a Communist. The Act Of Killing focuses on a select group of these former mass murderers, most of whom are now well into their 60s and 70s, who have been tasked with cinematically re-enacting their violent histories.

The documentary takes a solid hour to get up and running, flitting from place to place as we're introduced to these now mild-mannered "monsters". Exposing them not as extinct volcanoes, merely driven dormant by old-age, but still filled with the hate they possessed back in the day, and not an ounce of regret for what they've done. In fact most of them take pride in "being more cruel and savage than the Communists"; early scenes of them watching footage from their own movies fill them with shame, not for their actions, but because they don't like how they look on the screen.

However, during the last hour, when they are left to direct more and more re-enactments of their own heinous war crimes, you see that demeanour begin to crumble. Even as they hide their past behind a cinematic veneer of old-school gangster movies and big musical numbers, the realisation of their actions slowly begins to dawn of them, and it begins to take a startling emotional, psychological and, in some cases, physical toll on them all.

As you may have gathered, this is one heavy movie. Even as we watch ridiculous scenes of an overweight male transvestite trying to direct a flamboyant ghost on how to act scarier, it's still painfully clear that it's all a smoke-screen; this is self-described therapy disguised as movie-making. It takes a long time to get there, but The Act Of Killing ends up as one of the most disturbing, powerful movies of the year.