Two violent robberies on Merseyside and in Cheshire, in which the victims had boiling water poured over them, are to feature in a Crimewatch appeal.
Three masked men burst into a house in St Helens, Merseyside, on 4 November and tied up a couple in their 60s. The poured hot water over the man, 69.
On 27 September, four raiders burst into a house in Warrington, Cheshire, while a man was in the shower.
They threatened the victim, 44, with a pickaxe and threatened to kill his dog.
'Staked out area'
Police believe the robberies are linked.
In the St Helens incident, Tommy and Marian Bradshaw were sitting in the living room at about 1900 GMT when their front door burst open.
After tying up the couple and threatening them, the raiders demanded access to the safe.
Mrs Bradshaw, 64, gave them cash and jewellery but the raiders wanted them to open another one - which did not exist.
They then punched and kicked Mr Bradshaw, and poured water from the kettle over him.
Det Sgt Paul Grounds, of Merseyside Police, said he believed the robbers had "staked out the area" before the burglary.
He added: "It was a pre-planned and terrifying incident and we are determined to do all we can to catch the men responsible and put them behind bars."
In the Warrington incident, the victim was at home in Houghton Green at about 2100 GMT when he was confronted by raiders wearing balaclavas.
After threatening him and his dog, pouring boiling water over him, the robbers tied him up and fled with cash.
Anyone with information is asked to contact Merseyside or Cheshire Police or Crimestoppers.
Crimewatch will be shown on BBC One at 2100 BST.