'A tour de force, offering an original take on a neglected aspect of extremist radicalization: the strange phenomenon of extremist side-switchers. Koehler's gripping narrative account of defectors who migrate across extremist groups and ideologies is both absorbing and trailblazing, shedding important new light on critical vulnerabilities during de-radicalization and disengagement processes.' Cynthia Miller-Idriss, Professor in the School of Public Affairs and the School of Education, American University, USA