AD 171 Banna Fort, Hadrian's Wall
 
Centurion Aurelius Petrus reluctantly joins the secretive cult of Mithras.
 
Drawn deeper into its initiation ceremonies, Petrus must navigate the politics of the cult as well as their clandestine rituals. When the body of a man is found, Petrus is charged with the investigation. 
 
There Petrus uncovers theft, blackmail, and assault as he searches for the murderer. Unsure who to trust, he has to rely on his informant and the counsel of his wife Aurora, as he seeks to bring the culprit to justice.