Perpetrators of mass violence are commonly regarded as evil. Their violent nature is believed to make them commit heinous crimes as members of state agencies, insurgencies, terrorist organizations, or racist and supremacist groups. Upon close examination, however, perpetrators are contradictory human beings who often lead unsettlingly ordinary lives. Drawing on decades of on-the-ground research with perpetrators of genocide, mass violence, and enforced disappearances in Cambodia and Argentina, Antonius Robben and Alexander Hinton explore how researchers go about not just interviewing and writing about perpetrators, but also processing their own emotions and considering how the personal and interpersonal impact of this sort of research informs the texts that emerge from them. Through interlinked ethnographic essays, methodological and theoretical reflections, and dialogues between the two authors, this thought-provoking book conveys practical wisdom for the benefit of other researchers who face ruthless perpetrators. Research with perpetrators is a difficult but important part of understanding the causes of and creating solutions to mass violence, and Robben and Hinton use their expertise to provide insightful lessons on the epistemological, ethical, and emotional challenges of ethnographic fieldwork in the wake of atrocity.