From the back of the book:
A lost Prodigy...
Almost thirty years ago, a female wizard of the covenant bore a son and named him Andros. As he grew, the other magi realized that Andros understood magic at a level the scholars of Hermes could not comprehend. He knew the future and the past; he could see and speak with spirits. But then, quite suddenly, the youth acquired a great fear of magic, and soon thereafter ran away.
Today the name Andros is again spoken at the Covenant, when a mysterious message arrives from Byzantium. The letter reports that Andros lives as the slave of one Farad Sahda, "The Old Physician," a conjurer of the Black Sea. The letter's writer enjoins the covenant to rescue its offspring - who, with his master, will soon be in Constantinople.
Constantinople, the magnificent capital of the mighty Byzantine Empire, is but the first stop in this adventure of intrigue, mighty spirits, strange magic, and legendary places of Europe's Orient!