In January 2018, 37-year-old Paul Mathieson was found fighting for his life on a street in Renfrew. The victim of a brutal assault, Paul succumbs to his horrific injuries and the skilled investigators of Police Scotland’s Major Investigations Team take up the case. Despite the assault being caught on CCTV, the perpetrator is not identifiable and mysteriously disappears from the scene. Paul’s sister Amanda, a nurse at the hospital where Paul was taken, is enlisted to help appeal for information. For over five months some of the most skilled detectives in Scotland work tirelessly to try and identify the perpetrator. With a lack of any forensic evidence, vulnerable and unreliable witnesses the elements conspire against them.

Police Scotland’s major investigation teams deal with around 60 murders a year. This episode delves deeper into the nature of the job. Through gripping actuality sequences and in-depth interviews with both senior and rookie detectives, discover what it is like to work on such devastating cases like the murder of Alesha MacPhail and the disappearance of Julie Reilly. These are the men and women who go to the very worst crime scenes and deal with the very worst offenders, trying to find answers to situations that defy explanation. Their dogmatic pursuit for justice makes sure no stone is left unturned.