After the promotion to Police Scotland's Historic Cases Unit, Karen Pirie reopens the cold case of murdered barmaid. Her investigation unearths flaws in the original 1995 inquiry.

With suspects under attack, Karen’s cold case review has just become a live investigation overnight. But is the perpetrator Rosie’s killer, out to silence potential snitches? Or are they a wounded family member or friend, out to exact revenge? Finding the answer could give Karen her strongest hope yet of solving the case. In 1996, the discovery of an abandoned car leads to the arrest of one of the students, but with a lack of physical evidence, the investigation founders - until a potential eye witness brings DI Maclennan new hope. Exploiting the contacts of her best friend River in the hope of finding out more about a suspicious ex-partner of Rosie’s, Karen makes a shocking discovery.

Damning forensic evidence leads to a shock arrest and Karen brings the suspect in for questioning. But with only 24 hours to a build a case, is time running out? Bel’s call-out on the podcast brings forward an eye witness whose testimony leads Karen and Murray to a horrifying possibility. With a new lead to pursue that could change the course of the entire investigation, Karen is thrown into mortal danger. Forced to confront a version of the truth she’d never thought possible, and with everything at stake, will she finally find Rosie’s killer and achieve justice after 25 years?