When I moved to Moscow last year, most of my knowledge of Russia came from Helen Dunmore's historical novel The Seige, set in wartime Leningrad (now St Petersburg). This might not seem like much to start a relationship with a country, but the novel gave me the advantage of knowing something of the personal lives and habits (albeit fictional) of Russian people, underneath the impassive faces on the Metro.

After we're urged not to give away the plot during Q&A, Dunmore reads the beginning of her new novel The Betrayal, a sequel to The Seige which follows the same characters in post-war Leningrad just before Stalin's death. This is a time in Russian history, Dunmore tells us, when Stalin was becoming increasingly paranoid, particularly of doctors.

The reading is fluid. Dunmore has a reassuring style, and I'm engaged with the characters immediately through the spare dialogue of a complex interaction between two doctors set against an ominous medical backdrop. The oppressive atmosphere created by the hospital and the fear and tension between the colleagues is broken just in time by a switch of scene, and memory of both practicality and fertility. As always, Dunmore describes food and daily routine as sensual, weighty items.

The interesting thing about historical fiction, the author tells us, is that the characters have no hindsight. They are unaware that Stalin is about to die, and where this places them in history.

Having never lived in a terror state, Dunmore describes the task of creating an atmosphere of national terror as a three-part process: imagination, research and the intensification of the experiences everyone has. Research via diary and memoir was easy enough to come by, as was the topographical research of St Petersburg, as the author mapped routes for the characters around the city. There was a lot of historical material which was either destroyed or inaccessible due to extreme restrictions on information which still exist in Russia. An audience member who conducted research in the country commented that any material which indicated collaboration with Germany was kept out of sight.

The novel contains a theme of betrayal; both betrayal by the state, and the betrayal which occurs between people during times when there is a premium on information and denunciation. Dunmore does not write from a moral high ground, acknowledging that it's difficult to tell who would betray their neighbour in such a situation, and who would take risks to help a stranger.

This very reluctance to moralize might be why the author has been well received in Russia. The Seige has been translated into Russian and read on Radio St Petersburg.