Set during 1870s Victorian England, it tells the story of a woman, Margaret Prior, who is haunted by a shadowy past and in an attempt to cure her recent bout of illness and depression, begins visits to the women's wards of Millbank Prison.

Margaret Prior (also called "Peggy" and "Aurora"), an unmarried woman from an upper-class family, visits the Millbank Prison in 1870s Victorian-era England.

Margaret is generally unhappy, recovering from her father's death and her subsequent suicide attempt, and struggling with her lack of power living at home with her over-involved mother despite being almost 30.

She learns that this woman is Selina Dawes, who is a somewhat infamous medium of spirits jailed two years previously for the apparent death of the lady with whom she resided.

After their early discussions, Margaret begins to confide in Selina details of her past, and learn more about spiritualism; before long, the relationship evolves and appears to take on a life of its own...