In this episode, former Detective Chief Inspector with the Metropolitan Police Jackie Malton returns to her roots as a detective to re-examine the crimes of childhood friends – John Duffy and David Mulcahy – two of the most notorious rapists and murderers in British criminal history. What made their crimes distinctive was the fact they worked together – meticulously planning and executing crimes against women. During the 1980s, a series of violent rapes occurred across London, all with one common factor – they were located in and around quiet railway stations. All of the women talked of two men acting together and they soon became known as “The Railway Rapists”. Then, in December 1985, Duffy and Mulcahy took their first life – the victim was 19-year-old Alison Day. This would be the catalyst to two further murders committed in 1986 – of a 15-year-old Dutch schoolgirl Maartje Tamboezer and 29-year old Anne Lock. All three women were abducted in the vicinity of a railway station, then tortured and raped before being murdered. In the days before the coordinated police resources, none of the three separate police forces investigating these crimes were aware of the link between them. But when officers from the three teams appeared on national television appealing for information on their cases, “Operation Trinity” was born to coordinate the efforts. Jackie Malton meets key officers involved in the investigations, who have never been interviewed before, including retired Hertfordshire Detective Inspector Paul Dockley, and Chief Inspector Brian Roberts of the Metropolitan. She also interviews Psychologist David Canter to discover how the FBI-style criminal and geographical profiling were used during these investigations, for the first time in the UK history. In November 1986, John Duffy was finally charged after a long investigation, but there was sufficient evidence to convict him for only two of the murders – Alison Day and Maartje Tamboezer. He left his accomplice’s name out of the story, meaning Mulcahy walked free. But 10 years later, while still behind bars, Duffy began talking about his crimes in great detail to a psychologist, finally naming Mulcahy as his accomplice. A new case was opened. Jackie meets retired Detective Andy Murphy who headed up “Operation Marford” to re-examine the original convictions. In 2001, using DNA evidence and Duffy’s testimony, both men were separately tried and convicted of a total of fourteen rapes and murders of all three women – Alison Day, Maartje Tamboezer, and Anne Lock.