When Jihadi John was revealed to be Mohammed Emwazi from Britain, the author realized with great shock that this was the same young man he had interviewed several years earlier. Back in 2010, Mohammed Emwazi was a twenty-six year old college graduate who claimed security services were ruining his life. He and his family had been repeatedly approached and questioned. In the aftermath of the US air strike that killed Emwazi in November 2015, Verkaik's investigations led him to deeply troubling questions, among them, why do hundreds of Britons want to join the Islamic State?.