At the crack of dawn in residential Newcastle, a man is violently assaulted and stabbed in his home by two unknown assailants. The suspects flee the scene and it is the job of rookie CSI Nicola Stark to examine the crime scene and surrounding area to find the clues that could lead her to identify the attackers. In Sunderland, a woman reports being raped by two unknown men in a block of flats. Intimate samples are immediately taken as these provide the best chance of identifying the unknown suspects and bringing them to justice. But with two different, and as yet unknown people’s DNA present in the samples, identifying individual DNA profiles for comparison with the national DNA database is no simple matter.

In central Newcastle, a teenage girl has been raped by a stranger in a local park. It is the job of Northumbria Police's head of forensics Kirsty Potter and senior investigating officer Shelley Hudson to find the unknown suspect and put him behind bars as quickly as possible. With every hour that passes the chances of obtaining forensic evidence reduce and intimate forensic samples from the teenager who has been raped are fast-tracked to a specialist lab in order to try and identify the suspect. A scour of local CCTV identifies a man wearing the same distinctive jacket as the teenager described.

Alongside the traditional forensic search for body fluids, DNA and fibres, the police also deploy the rapidly evolving skills of their digital forensic team. Criminals may think they can withhold passwords and delete incriminating search histories from their computers, tablets and smart phones, but it won’t give head of digital media Jerry Hewitt and his team too much difficulty.