The first body comes as a shock The second brings horror The third signals the beginning of a nightmare When fifteen-year-old Isla Bell finds three bodies propped against Hadrian’s Wall, her whole world falls apart. In such a close-knit community, everyone knows the victims, and the man who did it. Twenty years on and Isla has dedicated her life to forensic psychology; studying the brains of serial killers, and even coming face to face with the convicted murderer who turned her world upside down. She is safe after all, with him behind bars. Then another body appears against the Wall. And another. As the nightmare returns and the body count rises, everyone in town is a suspect. Who is the Killer on the Wall?