Chilling CCTV footage showing a suspected arsonist in a ghoulish mask has been released by police.
The video shows a person wearing a Halloween-style disguise just moments after the attack in Castle Bytham, Lincolnshire, and a second person wearing a rucksack.
The suspect appears to deliberately stare into the camera.
An 82-year-old man and 74-year-old woman living in the property were able to escape, but police have said they could easily have been killed.
The couple's dog died in the fire, which is thought to have been deliberately started with a firework.
The house, on the town's high street, was damaged extensively by the flames.
Detective Sergeant Jon Shield from Lincolnshire Police said the CCTV footage - released more than a year after the crime - has been enhanced.
He said: "The original images were of very poor quality.
"We know that these ones are still limited in terms of not being able to see the face of the suspect, but you can make out a lot more detail on the mask and the rucksack worn."
Anyone with any information about the attack - which happened just before 3am on May 4, 2011 - can call Lincolnshire Police on 101 or Crimestoppers anonymously on 0800 555 111.