As an old house is demolished in a gentrifying section of London, a workman discovers a tiny skeleton, buried for years. For journalist Kate Waters, it's a story that deserves attention. She cobbles together a piece for her newspaper, but at a loss for answers, she can only pose one question: Who is the Building Site Baby? As Kate investigates, she unearths connections to a crime that rocked the city decades earlier: a newborn baby was stolen from the maternity ward in a local hospital and was never found. Her heartbroken parents were left devastated by the loss. But there is more to the story, and Kate is drawn - house by house - into the pasts of the people who once lived in this neighborhood that has given up its greatest mystery. She soon finds herself the keeper of unexpected secrets that erupt in the lives of three women - and torn between what she can and cannot tell.