We stumbled out of the ICA late on a Sunday night in filmic shell-shock. The crowd demonstrated a range of trauma, from stunned silence to blustering efforts at ordering thought. I was told one of our party had left halfway through. Not because of the gore, but because The Act of Killing's power hinges on horrific deeds being relived by all-too-human perpetrators. The honesty and black comedy of the confessions made in the film make for the most unsettling and self-conscious viewing as an audience I can remember since seeing Clybourne Park in the West End. In the 1960s, Indonesian gangsters were given license by the Junta of the time to suppress supposed Communists. The wholesale slaughter has never been redressed and those who led the killings are considered national heroes to the extent that director Joshua Oppenheimer had no problem getting an uncensored version of events. The Act of Killing's premise is otherworldly and devastating – ask these seemingly remorseless killers re-enact their actions in dance and film. The often surreal results have as much to say about storytelling as they do about the legacy murder leaves on the soul.