Sean Chancellor is shocked to learn that his colleague and friend Alex Zegliwski has been savagely beheaded. His body found in an underground archaeological dig, hidden beneath the holy temple of Hagia Sophia in Istanbul.When Sean arrives in the ancient city to identify the body, he is handed an envelope of photographs belonging to Alek and soon finds himself in grave danger. Someone wants him dead but why?Aided by British diplomat Isabel Sharp, Sean begins to unravel the mystery of the mosaics in the photographs and inch closer to snaring Alek’s assassin. Evil is at work and when a lethal virus is unleashed on the city, panic spreads fast. Time is running out for Sean and Isabel. They must catch the killer before it’s too late.