Detective duo Scott and Bailey are returning to TV in a three-part special being filmed later this year.
The pair, starring Lesley Sharp as DC Janet Scott and Suranne Jones as DC Rachel Bailey, will take on an web of killers who gather online to boast about their crimes and incite each other to commit more.
Jones' former Coronation Street co-star Sally Lindsay, who created the ITV show with the actress, will also return to play her sister Alison.
Executive producer Nicola Shindler, whose CV includes shows such as Happy Valley and Last Tango in Halifax, said: "We're delighted to be returning to Scott and Bailey with an investigation that will have everlasting consequences for the characters.
"This series is more ambitious and sinister than ever before and the concept of a three-part story allows us the opportunity to tackle a story of epic scale and ambition".
Filming starts in Oldham and Manchester in September.