On a snowy night in winter 1991, 15-year-old Vicky Hamilton fails to arrive home. Her case becomes one of Scotland's biggest missing persons investigations. Posters of Vicky smiling in her school uniform appear nationwide, but her family are left distraught when no trace of Vicky can be found. In an emotional new interview, Vicky's sister Lindsay recalls her memories of that time and the horrendous strain it had upon her family. 

Several days after her disappearance, Vicky's purse is found near a bus station in Edinburgh, leading investigators to wonder whether she wants to be found at all. In the summer of the same year, 18-year-old Dinah McNicol disappears after hitchhiking home from a music festival in Kent, and her father turns to the National Missing Persons Helpline for help. The early 90s are a period of change for how missing people are investigated, and the new charity highlights the plight of Britain's missing people and their families. The programme also reveals that a video by American rock band Soul Asylum would also be used to help the search for both Dinah and Vicky. 

Kaye Adams, along with other journalists and TV presenters, describe how these cases of missing people started appearing on television programmes including popular 90s chat shows and Crimewatch, leading to wider public attention. Vicky and Dinah's missing persons investigations result in no real leads for over 15 years, until 23-year-old Angelika Kluk goes missing in Glasgow in 2006. At the time of her disappearance, the Polish student is living in the chapel house of a church in the city, where she has a summer job as a cleaner. After some days, her body is found hidden under the floorboards of the church, in a case which shocks Scotland. 

Forensic biologist Carol Rogers describes how she must crawl under the floorboards to collect vital DNA evidence from the bloody crime scene. Meanwhile, police search for the man Angelika was last seen with - a church handyman by the name of Patrick McLaughlin. 

The manhunt for Patrick McLaughlin becomes nationwide news, and he is tracked down to a hospital in London. We hear from the doctor who was treating Patrick when the police arrived at the scene. By then his true identity was known to the police - he was an on-the-run sex offender known as Peter Tobin. Tobin's arrest set in motion a remarkable series of events that lead to the horrifying suspicion that a serial killer had been roaming at large in the UK for decades.