Between 1975 and 1979 the seemingly peaceful nation of Cambodia succumbed to one of the most bloodthirsty revolutions in modern history. Nearly two million people were killed. As head of the Khmer Rouge's secret police, Comrade Duch was responsible for the murder of more than 20,000 of them. Twenty years later, not one member of the Khmer Rouge had been held accountable for what had happened, and Comrade Duch had disappeared. Photographer Nic Dunlop became obsessed with the idea of finding Duch, and shedding light on a secret and brutal world that had been sealed off to outsiders. Then, by chance, he came face to face with him. "The Lost Executioner" describes Dunlop's personal journey to the heart of the Khmer Rouge and his quest to find out what actually happened in Pol Pot's Cambodia and why.