A man is released on licence after serving 20 years for the murder of a 14-year-old girl. When the body of her best friend, who disappeared at the same time, is found, Frost has to investigate a 20-year-old murder.

A bus driver and conductress are abducted. Frost is unhappy at being paired with DS Marsh, who made a complaint about him 15 years before.

Three naked bodies are found buried, and laid out in the shape of a triangle. Meanwhile, there is trouble when a multi-millionaire businessman decides to relocate his corporate headquarters to Denton.