Although Catrin is the rightful heir to the Celtic throne in Britannia, she is lucky to be alive. After witnessing the slaughter of her family at the hands of her half-brother, who was aided by the Romans, she is enslaved by a Roman commander. He disguises her as a boy in the Roman Legion with the belief that she is an oracle of Apollo and can foretell his future. The sole bright spot in her miserable new life is her forbidden lover Marcellus, the great-grandson of the famed Roman General Mark Antony. But Marcellus has been wounded and his memories of Catrin and their secret marriage were erased by a dark Druidess. Though Marcellus reunites with Catrin in Gaul and becomes her ally as she struggles to survive the brutality of her Roman master, he questions the legitimacy of their marriage and hesitates to help her escape and retake her kingdom. If their forbidden love and alliance are discovered, her dreams of returning to her Celtic home with Marcellus will be shattered.