DC Lisa Armstrong is asked to assist a murder investigation in Morecambe. The team try to uncover why the victim was targeted, but meanwhile, Lisa and her family are unknowingly stalked by a mysterious figure who has an agenda.

Determined to ignore Andy's unexpected arrival the night before, Lisa throws herself into the case and discovers a significant lead from her only eyewitness. The new information opens up the investigation and the team uncover vital evidence.

As the team press on with the investigation, Lisa and Med dig deeper into the family.

Following an unexpected turn in the case, Lisa and the team accept help from a new unit.

Lisa pursues a new line of investigation, uncovering a far-reaching secret.

As a confession brings the team closer to the truth, Lisa identifies a suspect.

After meeting the twins' parents, Lisa is shocked to discover that her connection to the family might be more than just professional.

With the Meredith family reeling from Dylan’s death and Sean’s arrest, Lisa is charged with finding his alibi and makes a game-changing discovery. Abbie grows closer to newcomer Vincent, whilst Rob agrees to take on a risky dare.

When the main suspect goes missing, Lisa is concerned about Sean’s possible involvement. Abbie falls deeper into Vincent’s world, bringing Sam with her. Meanwhile, Sean’s vigilante justice leads him down a dangerous path.

With Nick seriously injured in hospital, Lisa furiously seeks out Sean, while Med feels increasingly side-lined. Meanwhile, Rob attempts to leave the online forum, but finds that it is not as easy as he had hoped, and Sam tries to offer Abbie a way out from Vincent.

A confession to Lisa shines a possible new light on Dylan's killer. Meanwhile, Abbie has a terrifying experience with some local addicts, and Rob's escalating actions begin to impact on his family. Elsewhere, Med starts to suspect Lisa is hiding something from him and begins to make his own investigations.

Despite Holly's confession that she killed her brother, the team are convinced there's more to the story than she's telling them.