It's 1965 and 18 year-old Rosie Churchill has run away to the beautiful but run-down Castaway House in the seaside town of Helmstone. But when she uncovers a scandal locked away in the walls of the old house, she soon comes to realize that neither her own troubled past nor that of the house will stay buried for long. In 1924, fresh-faced Robert Carver comes to Castaway House to spend a languid summer in the company of his much wealthier cousin, Alec Bray. But the Brays are a damaged family, with damaging secrets. And little does Robert know that his world is about to change forever. As Rosie begins to learn more about Robert, the further she is drawn into the mysterious history of the house, and their stories entwine.