Innokentii Volodin, a diplomat, makes a telephone call to an old family doctor (Dobrumov) he feels obliged by conscience to make, even though he knows he could be arrested. His call is taped and the NKVD seek to identify who has made the call.
The sharashka prisoners, or zeks, work on technical projects to assist state security agencies and generally pander to Stalin's increasing paranoia. While most are aware of how much better off they are than "regular" gulag prisoners (some of them having come from gulags themselves), some are also conscious of the overwhelming moral dilemma of working to aid a system that is the cause of so much suffering. As Lev Rubin is given the task of identifying the voice in the recorded phone call, he examines printed spectrographs of the voice and compares them with recordings of Volodin and four other suspects. He narrows it down to Volodin and one other suspect, both of whom are arrested.
By the end of the book, several zeks, including Gleb Nerzhin, the autobiographical hero, choose to stop co-operating, even though their choice means being sent to much harsher camps.
Volodin, initially crushed by the ordeal of his arrest, begins to find encouragement at the end of his first night in prison.
The book also briefly depicts several Soviet leaders of the period, including Stalin himself, who is depicted as vain and vengeful, remembering with pleasure the torture of a rival, dreaming of one day becoming emperor of the world, or listening to his subordinate Viktor Abakumov and wondering: "...has the day come to shoot him yet?"
