The Lyell team investigate the clinical shooting of a mother, stepfather and son by the River Malt, to determine who killed this picnicking family and why. The investigation soon turns to the female victim's estranged husband. The couple were in the middle of a bitter and acrimonious divorce, and records kept by the deceased show that the husband has a propensity for violence.
Working on the case is local detective Malcolm Guillam, about to retire and haunted by the death of a young woman near the River Malt ten years ago. When the present day murder brings back memories of the unsolved case, Guillam sees an opportunity to redeem himself. But leading the investigation is DCI Butcher, who is certain the estranged husband is responsible for the murder, and has little time for Guillam's perceived trip down memory lane.
Meanwhile, registrar Amy is advancing in her surgical career when news of the River Malt shooting brings back memories of the same incident that haunts DS Guillam. Attempting to bury her past, Amy is unwillingly pulled back into the same world that caused the death of her friend ten years ago and forced to confront the high-powered people she has been trying desperately to forget.