Against the stunning landscapes of Scotland's iconic Loch Ness, local detective sergeant, Annie Redford finds herself in the midst of her first murder investigation; DCI Lauren Quigley is called in to lead the investigation, joined by forensic psychologist Blake Albrighton who believes there is more to the murder than initially meets the eye. Grief, terror, and suspicion soon shatter the town's normality.

Amanda Burton returns as forensic pathologist Sam Ryan in the first of three more 2-part stories. When two elderly Jewish brothers are found murdered, their deaths are linked to the suspicious death of another man. The only man arrested in that case had been a known racist who had attacked the two brothers' just months before.

In the concluding episode of the last story in this series, the nun who wants Sam to authenticate her Saint is keen to know the details of the post-mortem, especially as the future of the hospice depends on it. Meanwhile, Sam agrees to perform the second post-mortem on Helen Dupen requested by her mother, and continues to struggle with her illness.

Sam discovers that the Polish victim of a third apparently racially motivated attack was a member of the SS, and that there were traces of morphine in a glass found in his apartment. She realizes that the motive behind the murders was not racial, but revenge.

When her daughter's involvement in the Loch Ness Monster prank is revealed, Annie is disappointed to be off the case. Quigley focuses her questioning on Leighton Thomas, who was convicted of a double murder as a teenager. Forensic psychologist Blake Albrighton believes he knows the key to finding the killer.