Although known here for fictional features like 'Rice People', Rithy Panh is also a prolific documentarian who has striven to bring Cambodia's tragedy to a global audience.
This stark account of the atrocities committed by Pol Pot's Khmer Rouge in the Tuol Sleng interrogation centre is remarkable for the dignity with which painter Vann Nath (one of only three survivors of the 17,000 who were tortured at the ex-school that now serves as a genocide museum) confronts his persecutors in seeking to understand the motives that caused them to all but abandon their humanity.
The sequences in which the former guards recreate their daily routines are chilling, as is the realisation that the Angkar bureaucrats kept such meticulous records of their crimes. But those without prior knowledge of the Killing Fields will learn little about S21's secrets.