The Confidant, By Hélène Grémillon. Gallic Books, £7.99

Camille receives an anonymous letter. She has had various letters of condolence since the death of her mother, but this is very different. It is a typescript that recounts the childhood friendship of a young boy, Louis, and a girl, Annie, in a small French village during the early 1930s. What this has to do with a 35-year-old publisher's editor in 1975 is a puzzle. Is it fiction, sent by a would-be writer?

Further instalments arrive. Annie tells how in 1939 she meets a wealthy couple who have an estate in the village, their growing friendship, and the astonishing proposition that the wife makes. Madame M is infertile and proposes that Annie bear a child for her. The girl agrees and a room is prepared where Monsieur M can make love to her. She becomes pregnant after only one encounter.

Madame M moves her to Paris and Annie is hidden away, while Madame M simulates a pregnancy by padding her body. Annie gives birth in May 1940, but after only a month, Madame M seizes the baby and expels the mother. Annie has been so cut off from the world that the presence of German soldiers in the streets comes as a surprise.

Annie's account takes up the first half of this novel, as told to Louis shortly before her apparent suicide in 1943. The second half gives us the story as seen by Madame M, told again, somewhat unbelievably, to Louis. Her version is altogether blacker; a tale of emotional violence, hatred and revenge.

The trails laid in the past lead inevitably to Camille and long-buried secrets of her own family. If Camille remains a little sketchy, the past is skilfully and evocatively conjured, particularly the atmosphere during the Occupation.

The Confidant (translated by Alison Anderson) has the form of a thriller: the past that reaches into the future, altering lives; a destructive emotional war between two women; and a shocking twist of plot. That it is both more and less than a conventional thriller is down to Hélène Grémillon's writing: the plot creaks in places, but the inner lives of Annie, Madame M and Louis are perfectly captured and convincing. It is an impressive debut.