A man approached two people in The Mounts in Northampton before threatening one of them with a knife.
The victim and a friend were standing on the corner of Grove Road and Alcombe Road, near Queensgrove Methodist Church, when a man approached them from behind.
He threatened the victim with a knife and demanded he hand over his wallet.
The victim have him his wallet and the offender ran back down Alcombe Road.
The offender is described as black, about 6ft, with a muscular build and aged 30 to 40. He was wearing a black leather jacket, blue jeans, a black woolly hat and black trainers with blue straps.
The incident happened on Saturday April 12 at about 10.30pm.
Witnesses or anyone with information are asked to contact Northamptonshire Police on 101. Alternatively, information can be given anonymously to Crimestoppers on 0800 555 111.