A novel by the Strugatsky brothers, written in the genre of social science fiction. The action takes place on a planet at a stage of development reminiscent of Earth’s Middle Ages. The main character is the Earthman Anton, who works as an observer under the guise of the noble Don Rumata Estorsky. He faces a moral dilemma—to observe the cruelty and injustice without interfering, or to use his knowledge and technology to change the course of history.