"What Was Lost" is a novel by Catherine O'Flynn that explores themes of loss, memory, and the passage of time. The story revolves around the disappearance of a young girl named Kate in a shopping mall, which impacts the lives of various characters over the years. The narrative shifts between different perspectives, revealing how the event shapes their identities and relationships. The novel is set in Birmingham, England, and it highlights the changing landscape of urban life. Through its intertwining stories, "What Was Lost" examines how people cope with grief and the longing for connection in a world that often feels disconnected.