A police convoy escorting a civilian under a witness protection scheme is attacked. The witness is hospitalised and all police officers are killed – with the exception of Inspector Lindsay Denton, who organised the operation at very short notice and who only informed DCC Dryden. Ted Hastings asks Steve and Kate to investigate Denton, but Kate initially asks not to take part. She explains that she trained together with Jayne Akers, one of the dead officers, but she has also been having an affair with Jayne's husband, Rich. She is replaced by Georgia Trotman, an ambitious but less-experienced officer who is troubled that the team are treating Denton as a suspect and delving into her finances. However, she and Steve quickly grow close, while Hastings tries to keep up appearances with his estranged wife. Denton, shunned by her fellow officers, is transferred to a missing persons unit, and Kate, undercover once again, becomes her assistant. Kate follows Denton to the nursing home where her mother lives and sees Denton ring the hospital where the injured witness is being treated. Georgia and Steve race to the hospital and confront a man disguised as a nurse. Steve is knocked unconscious; Georgia, who sees the killer's face, is thrown out of a window to her death, and the witness is killed.