When the body of a young woman is dredged from a lake deep in the mountains of Snowdonia, DI Cadi John and DS Owen Vaughan are assigned to the case. They identify the victim as Mali Pryce, who disappeared five years earlier, when she was 16. Injuries on Mali's body suggest she had been running for some considerable time before meeting her fate. Cadi begins to explore the theory that Mali was held against her will during the five years that she was missing. Cadi's father is becoming unwell. Local labourer Dylan Harris faces hostile treatment from his mother Iona. The district nurse Lowri is seen to have a stormy relationship with her ex-boyfriend. Megan, a new student at Bangor University, is seen leaving a busy house party and walking to the Menai Suspension Bridge.