Selina March has lived in the remote Scottish hamlet of Inchcape, with its mysterious Round Tower, for nearly fifty years. When she reluctantly accepts a paying guest, her secluded life will change forever. Crime writer Joanna Savile has come to interview the inmates at Moy, the asylum for the criminally insane situated nearby. Her secret aim is to question former child murderer Mary Maskelyne, Moy’s most infamous patient. Joanna’s prying will yield unexpected results. For, although they have never met, Selina March and Mary Maskelyne are connected by a shared family tragedy: a terrible act of unspeakable cruelty that took place in India fifty years before. And there are secrets in Selina’s more recent past too. Secrets that are about to be unearthed with the most horrifying consequences.