September 1087-Simon, a physician, and Maura, his wife, live a life of precarious bliss in the cathedral village of Mynyw in Wales. At William the Conqueror's deathbed, William's family coerces him into releasing his vile brother Odo, Bishop of Bayeux, from prison. Odo blames Simon alone for his jailing, and his freedom unleashes a plague of devils. Their contagion of hate rages across England and Wales, leaving in its wake an endless horrific nightmare of invasions, murder, kidnappings, and poisonings, all of which abet Odo's ultimate aim-to destroy Simon and Maura's bliss forever.