In 1999, the media reported the arrest of Duch, aka the Butcher of Tuol Sleng--the most notorious torturer and executioner of the Cambodian genocide. Duch's unexpected arrest after years in hiding presented François Bizot with his first opportunity to confront the man who'd held him captive for three months in 1973, and whose strange sense of justice had resulted in Bizot's being the only Westerner to survive imprisonment by the Khmer Rouge. Only after his release had Bizot learned that his former captor--and, in a way, his only companion in those three months--had gone on to exterminate more than 10,000 Cambodians. Taking part in the trial as a witness, with Duch the sole defendant, would force Bizot to return to the heart of darkness. This is the testimony of what he discovered--about the torturer and about himself--on that harrowing journey.