DSI Stella Gibson is brought in to review the investigation into the murder of a woman in Belfast. As she travels across from London, we are introduced to the murderer himself: Paul Spector.

Gibson's worst fears are realised as Spector's murder spree in Belfast continues and a reckless decision has Gibson facing some very real consequences.

As Gibson takes control of the hunt for the serial killer striking against women in Belfast, the realisation that his perfect kill is tainted pushes Spector into looking for his next victim.

Gibson revisits the Sarah Kay crime scene. Ian Kay is keen to appeal to the killer's better nature and, despite her reservations, Gibson is keen to exploit this line of communication.

The killer's latest attack gives Gibson renewed impetus and as the net appears to be closing in, Spector makes a dramatic confession and a decision that binds his fate to Gibson.

Stella continues her hunt for the killer who hides in plain sight and is stalking the streets of Belfast.