Two men, one of whom was topless, hospitalised their victim for a number of days after they hit him on the head on the Racecourse.
The incident happened between 11pm on Sunday, May 6, and 1am on Monday, May 7 on the Racecourse in Kettering Road, when a man and his friend were approached by two other men outside The Picturedrome who became aggressive towards them.
They moved over to The Racecourse where the two men hit one of the other men on the head, causing injuries which required hospitalisation for a number of days.
A spokeswoman for Northamptonshire Police today said: "The offenders are described as two white men, one of which wasn’t wearing a shirt."
Witnesses, or anyone with information, are asked to contact Northamptonshire Police on 101 or Crimestoppers anonymously on 0800 555111.