International bestselling author Sophie Hannah creates a brilliantly sinister atmosphere in this psychologically and socially acute novel that explores the bond between mothers and their babies, the tragedies of crib death and infanticide, and the effect of incompetent pathologists.

Documentary producer Fliss Benson receives an anonymous card at work. The card has 16 numbers on it, arranged in four rows of four—numbers that mean nothing to her. On the same day, Fliss finds out she's going to be working on a documentary about miscarriages of justice involving crib-death mothers wrongly accused of murder. The documentary will focus on three women: Helen Yardley, Sarah Jaggard, and Rachel Hind.

All three women are now free, and the doctor who did her best to send them to prison for life, child protection zealot Dr Judith Duffy, is under investigation for misconduct. For reasons she has shared with nobody, Fliss has decided that this is her last project.

And then Helen Yardley is found dead at her home, and in her pocket is a card with 16 numbers on it, arranged in four rows of four...