The novel begins with an explanation of Leonid's few relationships within the revolutionary movement and the beginning of his relationship with Menni, a Martian in disguise. Soon after they become friends, Menni invites Leonid to go back home with him to Mars. The purpose of this visit would be to teach his own society to Martians and to understand and experience theirs. The trip is accomplished by the "etheroneph", a nuclear photonic rocket. On their way there, Leonid is exposed gradually to Martians and their society. With the help of Menni and Netti, his doctor, Leonid is able to speak the Martian language by the time they arrive.
At this point in the novel, Bogdanov details some of the aspects of the socialist Martian society as seen through Leonid’s eyes. Children’s colonies, factories, and housing are a few among the many aspects of this society that Bogdanov describes. Eventually, the unfamiliarity of Mars and the stress of his mission there exhaust Leonid to the point of being delusional. Just in time, Netti is alerted to his condition and treats him for his severe illness. While Leonid is recovering, he finds out, contrary to his original assumption, that Netti is female. His previous feelings for her are then expressed and they fall in love with one another. It is soon after this period that both Netti and Menni are called away for a mining expedition to Venus. While they are away, Leonid develops a relationship with Enno, another fellow shipmate from his arrival to the planet. While discovering many things about the nature of personal relationships on Mars, Leonid uncovers frightening information. He discovers that the council in charge of the Venus expedition was vying Earth’s colonization as a possibility. The argument presented, by Sterni (yet another shipmate), was that this was the only feasible solution and that it would only be made possible if Earth’s population was destroyed. As Leonid’s emotional state was not fully recovered from his exhaustion, this news sent him into a state of psychosis. His resolution is to murder Sterni, which he proceeds to do.
After this occurrence, Leonid is sent back to Earth to recover from his extreme apathy. He does so with the aid of Dr. Werner, an old comrade. Once he is able, Leonid rejoins the revolutionary fight, but this time with a mature perspective. The novel ends with a letter from Dr. Werner to Mirsky (a character assumed to be Plekhanov). In this letter, Leonid’s reunion with Netti is described and they are supposed to have returned to Mars together.