The non-linear plot, shifting back and forth in time from the 1940s to the 1960s, mainly concerns Andrew Hale, a scholar and occasional operative for a secret British spy organization.

Early in World War II, Hale is recruited as part of Operation Declare, an investigation of the true nature of several mysterious beings living on Mount Ararat, and how the Soviet Union has attempted to harness their vast supernatural powers.

The novel proposes that the Great Game, the prolonged geopolitical conflict between the British and Russian empires in the 19th century over domination of Central Asia, was actually part of Operation Declare.

While imprisoned in Moscow's notorious Lubyanka prison, she returns to her faith upon discovering the horrible motivation behind the deliberate mass starvation and violent political purges of Stalinist Russia: the placation of an entity called Zat al-Dawahi ("Mistress of Misfortunes") or Machikha Nash ("our stepmother"), a demonic being who demanded human sacrifice in exchange for protecting the nation from foreign invasion.

Powers's self-imposed rules prohibited him from disregarding established historical facts and timelines, instead finding alternate explanations for events (e.g., a real-life 1883 earthquake near Mount Ararat is part of the novel's backstory; and a peripheral comment attributed to British Army officer T. E. Lawrence by playwright George Bernard Shaw is interpreted as proof of Lawrence's involvement in Operation Declare.)