After a walker is found dead on a Welsh mountain trail, John's insight into the unidentified woman quickly turns this into a murder investigation. Janie ropes John into joining her mam Yvonne's walking group to help solve the case and crack the identity of this mysterious woman. John is reluctant to go out and socialise, but he can't resist the call of another mystery. John and Janie join forces to solve two mysteries: the identity of the victim and a cunning murder plot with a large dose of blackmail and revenge. Janie's fierce defence of one of the suspects reveals more about her past, while John finds himself out of the house and enjoying himself a lot more than he's ready to admit...