DCI Quigley is under pressure to wrap up the case but knows there are questions that remain unresolved. Struggling to answer these questions Annie discovers the evidence is flawed. The killer is still at large.

Annies determination leads her to uncover murder weapons used by the killer. She and Quigley join forces to hunt down the suspect.

As Annie becomes more entrenched in the investigation, Alan feels increasingly marginalised and their relationship begins to suffer. College Principal Craig Petrie is questioned as the main person of interest with his connection to Niall Swift and Jonjo.

With the killer still at large and a teenager with mental health issues now missing, the police come under further scrutiny.

Following the discovery of a human heart on the shores of the loch forensic psychologist Blake Albrighton is brought onto the team.

When a body is found at the foot of Carn Mohr Mountain, local detective Annie Redford is thrown into her first murder case.