An 86-year-old woman was pushed to the ground during a robbery at her home in Abbotts Langley, Hertfordshire.
The raider followed his victim home on Sunday before overpowering her and making off with a bag of shopping.
Det Con Andrew Roseblade said: "This was a distressing incident which left an elderly woman bruised and shaken.
"We are particularly interested in speaking to anyone who may have seen a small red car leaving the area at the time."
The suspect is described as white, with dark hair, aged in his 40s, of medium build and was wearing a green shirt.