A few families possess paper records stretching back through the centuries, but for most of us, family history is handed down from mouth to ear. These stories illuminate the past with a particular, fitful brilliance, but much is left in the dark. This darkness is both a gift to a novelist and a daunting responsibility. When a writer claims to speak for an illiterate woman who lived in the mid-19th century, to what extent will he overlay her story with his own preconceptions?

Although Gavin McCrea's first novel is set in the circles of Karl Marx and Friedrich Engels, this is not their story, and it does not flatter them. Engels and Marx left copious records behind them, but were unable to describe how they themselves might appear to a member of the working class, still less to a woman of that class. Nor did they tell the history of two sisters born in Manchester of Irish descent, Mary and Lizzie (Lydia) Burns, although both women were closely connected with Engels and Marx for many years. Neither sister left any account of their lives, but in they step forward to dominate the narrative.

McCrea's narrator is the younger, Lizzie, who was born in 1827. According to Marx's daughter Eleanor, Lizzie "was illiterate and could not read or write but she was true, honest and in some ways as fine-souled a woman as you could meet". Like her elder sister Mary, Lizzie worked in a cotton mill. Mary met Engels when he was sent to work at the family firm of Engels & Ermen in Manchester, and she entered into a relationship with him that lasted until her death aged 40. Some historians detect her influence on Engels' , which deals with the working class of Manchester and Liverpool, and describes in the district of Manchester known as Little Ireland.

The Burns sisters knew about poverty, child labour and slum housing from the inside, and would have made valuable guides for a middle-class son of a factory owner. "About 4,000 people, mostly Irish, inhabit this slum ... Heaps of refuse, offal and sickening filth are interspersed with pools of stagnant liquid. The atmosphere is polluted by the stench and is darkened by the thick smoke of a dozen factory chimneys," McCrea writes.

moves back and forwards in time, between the earlier days in Manchester and the later years after Mary's death, when Lizzie becomes Engels' partner in her sister's stead and moves with him to Primrose Hill in London. From the outside, she appears secure, but inside she is torn, even tormented, by the contradictions of her life.