As he fielded guilty pleas throughout 2015, Davis thought about how he might offer leniency to the conspiracy’s least culpable members. He could do so only if he knew for sure that the men would never again be tempted by jihadism. To that end, Davis began to research whether there are effective therapies for reforming extremists. He hoped to find a credible way to transform Yusuf and his friends back into the ordinary young men they’d once been. This could spare the youths years behind bars—an act of compassion that would undermine the Islamic State narrative that the West despises its Muslim citizens. ... Davis discovered that numerous nations, from Denmark to Indonesia, have developed methods for nudging young men and women back from the extremist brink—a process known as deradicalization. The judge became intent on starting the first laboratory for deradicalization in the US; he just needed to find an expert he could trust, someone with a proven track record of liberating young minds from violent extremism. ... Koehler’s key finding has been that all extremists, regardless of ideology, develop a sort of tunnel vision as they go through the indoctrination process. ... Koehler sees little point in starting moral or theological arguments with these young people, who are more interested in becoming warriors than debating the finer points of scripture. Instead, he advocates repluralization: the careful reintroduction of problems and solutions into a radicalized person’s life, so that they can no longer devote all their mental energy to stewing over their paranoia. ... Koehler believes that each client needs at least four mentors plus an “intervention coordinator” and that full deradicalization can be achieved only after a matter of years, not months.