"The best what-if thriller for a long, long time--makes you think, makes you sweat, and makes you choose, between what is and what might have been."--Lee Child

Istanbul, 1683: Mehmed IV, sultan of the Ottoman Empire, is preparing to lay siege to Vienna, capital of the Holy Roman Empire, when a mysterious visitor arrives in his bedroom--naked, covered in strange tattoos--to deliver a dangerous, world-changing message.

Paris, 2017: Ottoman flags have been flying over the great city for three hundred years, ever since its fall--along with all of Europe--to the empire's all-conquering army. Notre Dame has been renamed the Fatih Mosque. Public spaces are segregated by gender. And Kamal Arslan Agha, a feted officer in the sultan's secret police, is starting to question his orders.

Rumors of an impending war with the Christian Republic of America, attacks by violent extremists, and economic collapse have heightened surveillance and arrests across the empire. Tasked with surveying potential threats, Kamal has a heavy caseload--and conscience.

When a mysterious stranger--naked, covered in strange tattoos--appears on the banks of the Seine, Kamal is called in to investigate. But what he discovers is a secret buried in the empire's past, a secret the Sultan will do anything to silence.

With the mysterious Z Protectorate one step behind, Kamal, together with Nisreen--a fierce human rights lawyer--is caught up in a race across the empire and time itself--a race that could change their world, or destroy it.