Robbers chased a man who refused to hand over his wallet and stabbed him as he was asking a passer-by for help, police said this morning.
The attack happened was the man walked between Mounts Court and Fulleburn Court in Lumbertubs on Friday night.
A spokesman for Northamptonshire Police said: "Three men shouted at the 39-year-old, asking him to give them his wallet. The victim ran off and the offenders chased him along Fulleburn Court, across Penistone Road and into Sedgwick Court.
"Once in Sedgwick Court the victim approached a woman in a green Honda Civic to ask for help but the offenders caught up with him and assaulted him. The woman drove off.
"The victim was hit around the head, punched and stabbed in his leg. He was taken to hospital for treatment.
"The offenders went through his pockets and stole his phone, car keys and cash before making off," he said.
The incident took place between 11.45pm and midnight on Friday, and officers would like to speak to anyone who may have witnessed this incident. They would also like to speak to the woman who was driving the green Honda Civic.
The spokesman said the offenders were all black men, around 5ft 7ins to 5ft 8ins and of stocky build. All three wore dark clothing and had their faces covered.
Witnesses or anyone with information about this incident can contact police on 101 or Crimestoppers anonymously on 0800 111 555.