In the distant future, earthlings help less developed civilizations overcome the difficult stages of revolution. Anton, an employee of the Institute of History, goes to medieval Arkanar to save scientists who are capable of advancing evolution. He is to become Don Rumata Estorsky, a rich aristocrat who loves fights, drinking, and women. The main rule of the progressors is not to directly interfere with the natural course of history, selectively helping a few enlighteners avoid death. But Anton also has a personal interest, which he hid from the institute. Somewhere here, in Arkanar, his father has disappeared without a trace.