In the peaceful village of Old Sawrey, set in the idyllic Lake District, a murderer strikes. Warren Howe, a husband and father of two, is brutally slaughtered with his own scythe by a mysterious hooded figure. The police manage to identify several suspects, but due to the lack of evidence they fail to make an arrest.

Years later an anonymous tip-off sparks the interest of DCI Hannah Scarlett, who heads the local Cold Case Review Team. Scarlett's investigations lead her to suspect Howe's widow, Tina. Meanwhile, someone is sending vicious poison pen letters to Tina and her two children.

With the help of a historian, and his information on the goings on in his unusual garden, Inspector Scarlett delves deeper and deeper in her quest for the truth, discovering old sins that are casting long shadows. The clues are eventually pieced together, leading to a shocking revelation that will change Hannah's life forever.