Police believe the man in these CCTV images may have information about an alleged robbery in Portland Road, Rushden.
A police spokesman said: “A man was walking home after a night out when he was approached by another man who demanded money from him.
“He was punched and knocked to the floor.
“The offender then took cash from him before walking off.
“Officers would like to speak to anyone who may have witnessed this incident or who may have any information regarding it.”
The incident took place at about 1.30am on Sunday, March 19, although police have only just released these details about it.
Witnesses or anyone with information about the alleged robbery can contact police on 101 or Crimestoppers anonymously on 0800 555111.