Abyssinian Proof

19th-century Istanbul: a conspiracy to steal an ancient reliquary; a secret which could change the world.

The Ottoman Empire is plagued by thefts of antiquities from mosques and churches that, within days, appear for sale in Europe. Among them is a reliquary, presumed lost for four hundred years and around which an elaborate and mysterious sect has grown.

In Istanbul, magistrate Kamil Pasha is under...