This novel is based on the events and characters in history of 15th century Poland. The action of the novel is set against the background of the fate of Zofia Holszańska, the fourth wife of Władysław Jagiełło. Young Zofia, called Sonka in Ruthenian, staying at the court of the Grand Duke of Lithuania, Witold , is to become a tool of influence on the aging Władysław Jagiełło in his ambitious plans. With her help, Witold wants to gain significant influence over the king, portrayed as a weak and easy to manipulate ruler, and ultimately to implement his plan to break away from Poland and obtain the crown in Lithuania. However, it soon turns out that he underestimated her individualism, independence and her own political ambitions. Initially received with distrust, but quickly gaining sympathy, Sonka gathers a group of influential supporters around her, and emotionally attached to her new homeland and its ruler, she opposes her relatives insidious intentions, thwarting Witold's long-term plans. Moreover, by giving Jagiełło three desirable male descendants, she becomes the mother of future kings important in the history of Europe.