Between 1975 and 1979, the Khmer Rouge regime caused the death of some 1.8 million people. Kaing Guek Eav, better known as Duch, was in charge at M13 for four years before being appointed to the S21 centre in Phnom Penh where 12,280 people perished, according to the remaining archives. The first leader of the Khmer Rouge organization to be brought before an international criminal justice court, Rithy Panh records Duch’s unadorned words, without any trimmings, in the isolation of a face-to-face encounter. At the same time, he places it into perspective with archive pictures and eyewitness accounts of survivors. As the narrative unfolds, the infernal machine of a system of destruction of humanity implacably emerges, through a manic description of the minutiae of its mechanisms.