When Carol Jarvis vanished, doubts grew over her husband Harry's story - and sinister letters he sent his mistress did little to support his lies.
In 2003, Jane Longhurst vanished. Her body was found weeks later and police soon closed in on Graham Coutts, who Jane had planned to meet.
After killing his two children, Jordan Monaghan played the grieving father well. But a third death in 2019 saw detectives finally close the net.
After killing Billy Bryan and Annie Castle, Danville Neil escaped justice for 30 years, but advances in forensics eventually caught up with him, helping to convict the murderer in 2020.
In 1997, Nicholas Burton murdered Rachel McGrath in Stockport before abducting a student at knifepoint just hours later in Manchester. After a complex trial, the killer was found guilty and handed three life sentences.