Bulgaria. 13th century. The people, driven to utter despair, rise in arms. They elect Ivaylo - a poor peasant but gifted military commander - as their leader. Ivaylo's army overruns the Tatar invaders and the royal troops. In a decisive battle with the royal army, Ivaylo defeats and slays King Konstantin Asen. To prevent a betrayal on the feudal nobles, who intend to open the gates of the royal capital to Byzantine army, Ivaylo sacrifices his personal happiness, abandons his sweetheart and agrees to marry the widowed queen.