A man armed with a knife forced his way into a house in Chorley and demanded money.
Police are appealing for help to find the man who rang the doorbell at a detached bungalow on Sutton Grove shortly before 8.30pm on Friday.
A 57-year-old woman answered the door and the man pushed his way inside, brandishing a knife and demanding money.
He stole £80 in cash.
The man was described as white, aged 20 to 25, 5ft 10ins tall and of a medium build. He had short dark hair and a black lettered tattoo on the left side of his neck.
He wore a scruffy white T-shirt, blue jeans with two front pockets and a rear pocket, and scruffy dirty trainers with a velcro fastener.
The man had a black-handled peeling knife and spoke with a Liverpool accent.
Det Con Liberty Wadsworth, of South CID, said: “The aggrieved has been left distraught by this incident and I would appeal to anyone who has witnessed anything suspicious or who has any information to contact us.”
Anyone with information is asked to contact police on 101 or Crimestoppers, anonymously, on 0800 555 111.