A teenage boy was threatened by two men and forced to hand over his mobile phone in the Eastern District of Northampton.
The 17-year-old was followed by the offenders down Kelmscott Close from Dryleys Court sometime between 10pm and 10.30pm on Tuesday, April 25.
One of the culprits also tried to get the victim to hand over the jacket he was wearing, but left without it.
The first offender is described as black, around 18 years old, 6ft 3in tall and of a medium build.
He was wearing a black hoodie with the hood up and a black ski mask or balaclava as well as black gloves.
The second man is described as 6ft tall and of skinny build. He also had his hood up, and was wearing a grey hoodie which featured a cat emblem on the chest, which may be the Slazenger logo.
He was wearing a green zig zag pattern scarf over his face, and wore dark blue jeans and black Nike Air Max trainers.
Anyone with information can contact Northamptonshire Police on 101, or Crimestoppers anonymously on 0800 555 111.