The plot of Dmitry Bykov’s novel “Ostromov, or The Apprentice of a Sorcerer” is based on the now half-forgotten “Case of the Leningrad Masons” of 1925–1926. But it—just as often happens in this writer’s books (let’s recall the novels “Orthography” and “Justification,” with which “Ostromov” forms a kind of trilogy)—became only a backdrop for a many-layered narration about people’s fates in a turning, pivotal era; about rapidly changing criteria of good and evil; about perseverance that seems like a bravado; and about conformism that begins to take on the status of virtue. And it also raises questions about whether we, too, might have to experience something similar.