Criminologist David Wilson and guests dissect the importance forensics play in solving cases, and whether scientific advancements could be the key in solving decades-old cold cases.

David travels to the wealthy district of Broughty Ferry, Dundee, where he unearths a crime with multiple plot twists. This is the story of wealthy spinster Jean Milne, who was found murdered in her family mansion. The house in which she was murdered was found to be locked up tight, and one of her last sightings was with a mysterious German gentleman. Could Jean have been swindled by this foreign gentleman? It is a case shrouded in mystery, but one that might have been solvable had forensic science been as advanced as it is today.

Back in the studio, David meets with Professor Niamh Nic Daéid from Dundee University. Niamh, along with her colleagues, was commissioned to re-examine the 1912 Jean Milne case through a modern forensic perspective. Niamh talks David through their reinvestigation and the ways in which forensic science has progressed since 1912.

David is also joined by forensic scientist Helen Meadows. Helen dissects both Jean's case and the case of Mary McLaughlin, whose murder was solved almost 40 years later thanks to advancements in forensic analysis. Helen looks into the complexity of analysing DNA and how far we have come.

David's final guest is Joanne Cochrane, who, with her team, has worked with a new form of DNA analysis that could revolutionise the solving of a number of cold cases. Without her diligent work, it is unlikely they would have caught Mary McLaughlin's killer. Joanne breaks down the complexity of Mary's case and how DNA 24 works, and explains why these modern advancements in DNA are helping many cold cases to be solved.