In the distant future, people from Earth help less developed civilizations overcome difficult stages of their development. Anton, an employee of the Institute of History, travels to the medieval world of Arkanar to save scholars who could help advance progress. There he must become Don Rumata of Estor, a wealthy aristocrat known for fighting, drinking and women. The main rule for progressors is not to interfere directly with the natural course of history, but only to save the few enlightened people from death when necessary. But Anton has a personal motive that he has hidden from the Institute: somewhere in Arkanar, his father has disappeared without a trace.