Of the 17,000 individuals imprisoned and interrogated during the Khmer Rouge era at the notorious Phnom Penh camp Tuol Seng, only three survive today. Rithy Panh's moving documentary returns with two of them to meet the “other side,” their former guards. With the tables turned, the two survivors, one a writer, the other an artist whose remarkable paintings lend both reality and nightmare to the film, become questioners, asking those who once interrogated them what caused them to kill. “You killed without humanity,” they say to one former jailer, who responds merely, “I was young.” In a manner so unemotional as to be beyond horror, the guards explain how prisoners were tortured and killed, read from their “interrogation journals,” and reenact the routines of atrocity for a camera that becomes not only recorder, but witness.