This disturbing programme looks at perhaps the most devious and dangerous group of all offenders - the ultra-violent sexual predator.The crimes of two particularly vicious sexual killers are examined. The first story revolves around the shockingly brutal triple homicide of a woman and her two young daughters in Dalston, London in 1982. The killer – Wilbert Dyce - remained undetected until a cold case review was launched twenty-seven years later. The case was eventually solved by a combination of old-fashioned detective work allied with ultra-modern policing methods, such as DNA analysis and fingerprint comparison techniques. The police officers involved tell the gripping story of how the murderer – who tried to put police off the scent with graffiti suggesting it was a racist murder - was eventually brought to justice.The second story is centred around the horrific murder of Clare Benson Jowry in Lancaster in 2004. Clare was attacked by Paul Culshaw, a serial offender against women, whose many previous attacks are detailed by the investigating officers, as they build a picture of Culshaw's propensity for extreme violence.The film includes powerful testimony from surviving victims of both killers, and also includes expert analysis from a renowned criminal psychologist and an eminent forensic scientist, who examine and dissect both killers' motives and methods. The result is a chilling account of the horrifying crimes of two of Britain's most ultra-violent sexual predators – both of whom are now serving whole-of-life tariffs and who die behind bars.