The truce between Constantine, emperor in Rome, and Licinius, emperor of the east, has failed and Aurelius Castus is in the frontline once more. He is ordered to take command of the military forces of one of the western provinces now forming the domain of Constantine's teenage son, Caesar. But trouble looms on every side, both at home in his difficult marriage and on the battlefield, where he must decide once and for all whose side he is on. Will he back the pro-Christian emperors Constantine and Crispus? Or lead an insurrection against them, back to the old gods and the old ways?