The civilised world has been rocked by a sudden surge of terrorism. Extremism has proliferated even in the countries in the shores of the Mediterranean, which are meant to be that bit more sophisticated than their hinterlands. Suicide bombers spread terror in the streets of previously buzzing cities. Ashen-faced religious leaders condemn horrific acts committed in the name of their faith. Sound familiar? But this isn’t the world as we know it. Harry Turtledove takes us into an alternate reality in which Islam, not Christianity, became the dominant religion of the world in the medieval period. Now, progressive, modern and comfortable Muslim nations look warily at their Christian neighbours, and two brilliant investigators are dispatched to the dangerous streets of Italy in an effort to nip the terrorist threat of the Aquinists in the bud.