A knife is found near the crime scene that could be the murder weapon and while forensic analysis reveals the presence of DNA on the blade which might be from the killer, there's a one in 12,000 chance that anyone will match the DNA - which means as many as three people in Wisbech could be the killer. While the town's rumour mill continues to accuse previous suspects, DI Dale Mepstead has a difficult decision to make: will she arrest again? The sudden death of the original suspect is followed by the discovery at the murder victim's house of a large quantity of heroin and paperwork which suggests the illegal sale of prescription drugs. At last, an opening up of the mystery of a murder motive allows the detectives to move in to question their final suspect.

In Bedfordshire, police detectives discover a connection between a major fraud on a vulnerable old man's life savings and a gang who are exploiting young people. As cameras follow every twist and turn of two very different types of police operations, the true extent of the damage that the drugs trade wreaks are exposed in the most surprising ways.