1949 It is the coldest winter Orcades Island has ever known, when a pregnant sixteen-year-old arrives at Fairmile, a home for 'fallen women' run by the Catholic Church. She and her baby will disappear before the snow melts.

2013 Frankie Gray has come to the island for the summer, hoping for one last shot at reconnecting with her teenage daughter, Izzy, before starting a job as a deputy sheriff. They are staying with her mother, Diana, at The Fairmile Inn, soon to be a boutique hotel, but when an elderly nun is found dead in suspicious circumstances, and then a tiny skeleton is discovered in the grounds of the house, Frankie is desperate for answers.

At once an evocative, unsettling tale of past misdeeds and a crime thriller that will have you reading with your heart in your mouth, The Only Child is compulsively addictive storytelling from the bestselling author of The Botanist's Daughter.