The Rainbow Swamp is the fear of all magicians of the Middle Principalities. She drinks strength from people, breaks bones. Who sent a terrible curse to peaceful lands? Bloody Prince Vladislav, the ruler of the rich Cherna, a black witch, an apostate of the right faith, or a herbalist girl endowed with an unusual gift? Although there is not a drop of witchcraft in the blood of the herbalist Agnieszka, the villagers are ready to raise her with pitchforks. Salvation comes suddenly - the fugitive is carried away from trouble on a black stallion by the handsome magician Ilarius. But soon everything will change and he himself will need the girl’s help. And she has her own scores to settle with the rainbow...