The earth has become the epitome of a humanistic utopia. Rudolf Sikorsky, the head of the Commission for Contacts with Extraterrestrial Civilizations, instructs Maxim Kammerer to find Lev Abalkin, a progressive who mysteriously disappeared after contact with the supercivilization of the Wanderers. Abalkin's group explored the planet Nadezhda, which perished as a result of a monstrous experiment conducted there by the Wanderers. After contacting them, Abalkin kills his partner and flies to Earth to start a process similar to the one that destroyed Nadezhda. Kammerer manages to get on Abalkin's trail, but he is always one step ahead of him.