In the war-torn, chaotic fifth century, after the end of Roman rule and before King Arthur's rise to power, Celtic Briton Marcus ap Iorwerth diligently works to place the rightful high king in control of Britain. One of his duties, discrediting brokers of foreign mercenaries, leads him to Claerwen, an ethereal woman whose gift of visions draws him into the path of gods, a destiny as unshakable as the love they come to share.

In time, they realize Claerwen has inadvertently become ensnared in a lethal conspiracy involving the priceless sacred symbols of Britain's high kings, known collectively as Macsen's Treasure. Marcus makes every effort to protect her against a mazelike network of unknown enemies, but he is betrayed and disappears. Alone and homeless, Claerwen must decide whether to believe what everyone tells her, that Marcus is dead, or to follow her heart and the path of gods on a daunting quest to find him and the truth of Macsen's Treasure.