S21: The Khmer Rouge Killing Machine. Rithy Panh, himself a child victim of Pol Pot's reign, has gathered two survivors of the S21 detention centre (there are only three, even though 17,000 people were brought here) and several of their former guards. In the deserted building - now a genocide museum - torturers and victims try to talk to one another, with the former also explaining to Panh how their programme of confinement, torture and extermination was carried out. Former interrogators are now interrogated by the eloquent survivor Nath, and in their answers - as in their ritualised re-enactment of their former actions - we see the dehumanisation process still in action: the indoctrinated cannot admit responsibility, and so their victims, in turn, can never move on.