Detectives investigating the murder of a 96-year-old woman at a Lancashire care home have said they believe the killer will have confided in someone.
Edith Stuart's bed was set alight at Cleveleys Park Rest Home, in Cleveleys, on 18 October last year.
She died in hospital the following day. Six other residents were also injured.
Det Supt Neil Esseen, leading the investigation for Lancashire Police, will appear on the BBC's Crimewatch later to appeal for more information.
"We are hoping an appeal on Crimewatch could provide us with that crucial piece of information that could help us solve this case," he said.
"I find it impossible to believe that the person or people who did this would have been able to keep this terrible secret to themselves.
"It is likely they would have confided in someone about what they did.
"It is vital that those who hold the key to this investigation come forward to give Mrs Stuart's family the answers they desperately need."
Mrs Stuart's daughters Shirley Fish and Jean Worgan have been filmed for the programme talking about the impact of their mother's death.
Mrs Fish, from Poulton in Lancashire, said: "I thought some day she would just go to bed and go to sleep and that would be the end of a really good life and we could really celebrate it.
"We did try to celebrate that fact at her funeral but it was always at the back of it, the feeling that she had been murdered.
"How can we celebrate the end of a life when it is by murder?"
A 29-year-old woman and a 17-year-old girl, both from Cleveleys, were arrested on suspicion of attempted murder but later released with no charge.
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