For a young woman in medieval Russia, the choices are clear: a marriage proposal or a life in a convent. Vasya chooses a third path: magic. The court of the Grand Prince of Moscow is plagued by power struggles and rumors of unrest. Meanwhile, bandits roam the land, burning villages and kidnapping daughters. When the prince and his loyal companion set out to defeat the robbers, they encounter a young man riding a magnificent horse. Only Sasha, a priest trained as a warrior, recognizes this 'boy' as his younger sister, who is believed to be dead or a witch by their village. However, as Vasya proves herself in battle, riding with remarkable skill and inexplicable strength, Sasha realizes that he must keep her secret, as she may be the only hope to save the city from both human and fantastical threats.