Coventry, 1939. Days before the outbreak of World War II, a terrorist bomb explodes on a busy street, killing and maiming innocent civilians. A man is hanged on the evidence given by a young witness. As time goes on, the witness doubts her recollection of events, but her testimony has already had far-reaching consequences. Over sixty years later, in the wake of the 7/7 London bombings, Sara returns to her childhood home to find that her sister, Polly, missing for more than ten years, has finally come back too. Why now--and where has she been? The sisters grew up under the fierce protection of their nanny, Bridie, herself haunted by a family secret. And there are other secrets that Bridie has kept from the two girls she brought up as her own. Polly's return sets in motion events that will stretch the women's fragile bond to its breaking point.