 Dramatised documentary which describes the police investigation that led to the conviction of David Mulcahy for the notorious Railway Murders in the 1980s of three young women in the London area and for the rapes of many others. This investigation was based largely on the testimony of John Duffy to a psychologist in prison where he was serving life after being convicted of the same offences ten years earlier, having denied at the time of his trial that he had had an accomplice (Mulcahy).