Between October 2014 and November 2016, global terrorism expert Jessica Stern held a series of conversations in a prison cell in The Hague with Radovan Karadzic, a Bosnian Serb former politician who had been indicted for genocide and other war crimes during the Bosnian War and who became an inspiration for white nationalists. Though Stern was used to interviewing terrorists in the field in an effort to understand their hidden motives, the conversations she had with Karadzic would profoundly alter her understanding of the mechanics of fear, the motivations of violence, and the psychology of those who perpetrate mass atrocities at a state level and who—like the terrorists she had previously studied—target noncombatants, in violation of ethical norms and international law. How do leaders persuade ordinary people to kill their neighbors? What is the “ecosystem” that creates and nurtures genocidal leaders? Could anything about their personal histories, personalities, or exposure to historical trauma shed light on the formation of a war criminal’s identity in opposition to a targeted Other? In , Jessica Stern brings to bear her incisive analysis and her own deeply considered reactions to her interactions with Karadzic, a brilliant and often shockingly charming psychiatrist and poet who spent twelve years in hiding, disguising himself as an energy healer, while also offering a deeply insightful and sometimes chilling account of the complex and even seductive powers of a magnetic leader—and what can happen when you spend many, many hours with that person.