In 1984, Dr Alec Jeffreys, a University of Leicester scientist, unlocks a remarkable technique to read every individual's unique DNA fingerprint; four miles away, DCS David Baker is a tenacious detective searching for the murderer of a schoolgirl.

DCS David Baker searches for the murderer of two schoolgirls.

In 1983 Lynda Mann is found dead, a year later they still haven't found the killer and DCS David Baker is forced to scale back the investigation.

A young man is arrested after confessing to murder. DCS Baker approaches Jeffrey at the university after reading about his work and thinking it could help his investigation.

In order for the manhunt to work, DCS Baker & his team need the whole community to believe in the science & get behind the idea. They hold a town hall meeting to explain the idea to the sceptical villagers.