DCS Ian St Clair is called to investigate a tragic and unexpected murder in an ex-mining town as news of the crime threatens to inflame historic tensions.

As the hunt for the killer continues, Kevin Salisbury from the MET arrives to assist in the investigation; tensions mount as the killer torments the community further.

As Ian and Kevin are called to the scene of a second murder, news breaks of a former spy in the community at Gary's memorial service; Scott remains at large.

With two killers now on the run, Ian is forced to call in the MET to support the manhunt; the hunt for the mystery spy cop intensifies as a link to Scott is found.

As the manhunt closes in on Scott and Andy's location, the search for the spy cop turns the clock back to 1984 to reveal their identity and the events of that fateful night.

In a bid to protect those involved, Ian finds himself determined now more than ever to find the spy cop. The community attempts to heal in the wake of its loss.