The Camino de Santiago de Compostela, now the most famous pilgrimage route in the world, was founded in the early ninth century, largely due to the efforts of Bishop Theodemir of Iria Flavia. As with most people of this period, nothing seems to be known of his early years. What follows, therefore, is pure invention.

Theodemir returns footsore and disillusioned to his uncle's villa in Iria Flavia, where he meets Agnes, his uncle's gatekeeper, a woman of extraordinary beauty. He falls immediately in love. But Agnes has a fierce, though absent, husband; a secret past; another name, Elswyth; and a broken heart.

Witteric, Theodemir's cruel and lascivious uncle, has his own plans for Agnes. When the king of Asturias asks Theodemir to undertake an embassy on his behalf to Charles, King of the Franks, the future Charlemagne, Theodemir plans to take Agnes with him to keep her out of Witteric's clutches.

But though Agnes understands her danger as well as anyone, she refuses to go. And Theodemir dares not leave without her.