It's 1969. Five years ago, teenager Alexandra Tozer was murdered. Her sister, Helen Tozer, will never forget. Returning home after quitting the Met Police, she brings with her the recovering Detective Sergeant Cathal Breen, who slowly becomes possessed by the unsolved case. But Breen is on a trail, for the two men connected to this case met in Kenya, during the Mau Mau uprising; and the history that Britain has turned its face from is now returning to haunt it.