February 1098. The victorious march of the Crusaders across Asia Minor was stopped at the impregnable walls of ancient Antioch, captured by the Turks. A long and fruitless siege leads to the fact that in God's army, exhausted by disease and hunger, skirmishes begin between the Franks, Normans and Byzantines.

In this turbulent situation, one of the Norman knights is brutally murdered. His master Bohemond of Tarentum is eager to find the murderer and entrusts this case to the revealer of secrets, Demetrius Asciatus, who became famous for uncovering a conspiracy against the Byzantine Emperor Alexei. During the investigation, Demetrius suspects that the murdered man belonged to some mysterious sect and was sacrificed to an unknown pagan idol...