Sigwulf, a minor Saxon prince, is saved from execution after his family is slaughtered by the ruthless King Offa of Mercia. Thanks to his Devil's Mark - his eyes of different colors - Sigwulf is exiled to the Frankish court of King Carolus, the future Charlemagne. There Sigwulf survives on his wits while at the same time trying to come to terms with disturbingly prophetic dreams.

He gains the friendship of Count Hroudland, Carolus's powerful and ambitious nephew - but, mysteriously, several attempts are made on Sigwulf's life. When he obtains a Book of Dreams, a rare text that explains their meaning, he attracts the attention of Carolus himself. But th Book proves to be a slippery guide in a world of double dealing. Sent into Spain to spy on the Saracens, Sigwulf becomes caught between loyalties; either he honors his debt to new Saracen friends, or he serves Count Hroudland in his quest for glory, gold and even the Grail itself.

One after another Sigwulf's predictions come true, but often not as expected, and he finds himself swept forward into a final great battle that reveals who his enemies are...