Murdered pensioner Una Crown was stabbed several times before being set on fire.
The 86-year-old's body was discovered at her home in Magazine Lane, Wisbech, on Sunday.
A post-mortem examination revealed she died as a result of stab wounds to her neck and chest.
Mrs Crown's clothing had also been set alight.
Detective Chief Inspector Jon Hutchinson said:
– Detective Chief Inspector Jon Hutchinson, Cambridgeshire Police
"This was a horrific murder of a defenceless elderly woman in her own home."She was stabbed several times then set on fire in an apparent attempt by her killer to hide her injuries and destroy evidence."The fire damage meant it was difficult to initially establish the cause of Mrs Crown's death. However the stab wounds were revealed during the post mortem on Tuesday evening."I would appeal to anyone who thinks they may know who is responsible for this brutal murder."Did a friend or loved one come home on Saturday night or Sunday afternoon smelling of smoke?"I would urge you to do the right thing and call police to ensure the killer is caught and brought to justice."