A robber on a BMX bike threatened a man with a knife as he walked along Wellingborough Road in Northampton.
The victim was close to the Norman Road junction, heading towards Weston Favell, when the suspect pulled in front of him, pushed and punched him before demanding money.
The victim refused, despite the robber showing him a knife. The suspect then rode off in the direction of Weston Favell.
The suspect is described as a white man, aged in his early 20s and between 5ft 7in and 5ft 8in with a stocky build and a crew-cut hairstyle which was light in colour.
He was clean shaven and was wearing knee length shorts, but no top.
Witnesses or anyone with information about the incident, which happened between 9.20pm and 9.40pm on Saturday, August 6, can contact Northamptonshire Police on 101. Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555111.