313 AD. At the dawn of the fourth century, the Roman empire is beset by economic problems, barbarian incursions and religious divides. After a series of tyrannical rulers, Emperor Diocletian has divided the empire into east and west. Now, with Constantine's victory over Maxentius in the west, Rome finally appears to be emerging from its turbulent past. But instead of enjoying the fruits of his victory, Emperor Constantine is in trouble. In order to consolidate his power and under the guidance of his mother Helena, he plans to harness the power of the increasingly influential Christian Church. Then a series of murders brings his loyalties into question. The emperor frequents courtesans from the Guild of Aphrodite, three of whom have been found dead - all with crosses etched on their foreheads and each cheek. In order to protect her son's future, Helena, aided by the priest Anastasius, calls upon the service of an 'agente in rebus politicis' - or spy. Claudia is the niece of a tavern-owner and is placed as a wine-server in Constantine's household. But Claudia has secret motives of her own...