The team attend a triple murder at a farmhouse, where the investigating detective, DI Connie James, wastes no time making her presence felt. The pathologists soon make a breakthrough when DNA found at the scene matches that of a mysterious female serial killer - although Nikki has cause to question the direction they are heading in. The case is proving difficult for Leo, however, whose mind is in turmoil following the suicide of an old friend. Harry persuades Connie to disobey orders and test DNA evidence from the original investigation, and Janet is called in to help build the personality of the female serial killer. Leo is still troubled by the suicide of his friend Lizzie Frazer, prompting Nikki to dig deeper into the murder of the woman's sister ten years before.