The Betrayal, By Helen Dunmore

Helen Dunmore's 2001 novel, The Siege, ended with a long-shot of Anna, her lover, Andrei, and little Kolya, Anna's brother, walking in spring sunshine in a Leningrad still traumatised by the recent German blockade. They look like an ordinary family of parents and child, the narrator observes, "but, of course, they are not". These, the novel's unsettling last words, point towards the most important theme of its sequel, The Betrayal. For Anna and Andrei, their "family unit" is a precious, sanity-saving defence against public tyranny. But it is not, of course, unassailable.

Andrei, a Leningrad paediatrician in 1952, makes an innocent target for a craftier colleague, Russov, who shifts onto him the delicate task of caring for Gorya, son of a promoted official, Volkov. The latter, rewarded by Stalin for anti-Semitism, represents a tentacle of the "Doctors' Plot". Choosing medical skill over political expediency, Andrei employs a Jewish surgeon to operate on Gorya's osteosarcoma.

Anna is still a kindergarten assistant and, as in The Siege, alienated by an over-zealous boss. A skilful amateur artist, she had intended to enter her drawings in an exhibition of Leningrad art: she was glad she hadn't, because the exhibition was closed down by the authorities, and her work would have been lost. Unlike the protagonists of 19th- and early 20th-century Russian novels, neither Anna nor Andrei has time for soul-searching. They are devoted to their daily work, not to asking questions. Their political dream would probably be a "culture of content" much like the British dream of that post-war period

If the feast of ideas is sparse, Dunmore finds a compensatory richness in sensory experience. Every event is registered on the pulse, and often in the nostrils. The tactile qualities of an old, cherished piece of silk, the fragrance of soup or honey, the reek of a prison latrine, all register with eye-watering immediacy. It reminds us that even political animals are animals – responsive, glandular, vulnerable - and the ability to convey the significance of the ordinary is one of Dunmore's greatest assets. Ultimately, and almost satisfyingly, we see Volkov himself become the victim. As Gorya lies near death, Stalin drags his father out "on the town" to dance and party. Afterwards, Volkov sits with Andrei, smelling of drink, already destroyed under his mask of control.

There is no question that he is morally appalling, and none that evil has its own pathos. Dunmore's powerful, subtle dialogue connects the two Siberians, Andrei and Volkov, in a way that shocks, surprises and moves us.

Dunmore writes beautifully about children. Gorya, spoilt, sulky and almost heroically "in denial" about his illness, is hauntingly portrayed. Every word and gesture feels exactly observed and true. While the hope of a family of her own brightens with Anna's pregnancy, the secret police closes in on Andrei. As in The Siege, Anna must fight for her own and a child's survival. Again, the conclusion is carefully inconclusive. Anna believes, if only momentarily, that "one day Andrei will see his child". Meanwhile, she has begun to draw again. She has already buried the papers belonging to her quietly dissident writer-father. Such records, like the child, guarantee the future – and perhaps, happily for Dunmore's readers, also a third book?

Carol Rumens's latest volume of poetry is 'Blind Spots' (Seren)