A teenager was punched in the head after trying to help a girl who had collapsed on the floor in front of him.
The 18-year-old was standing outside a shop in Stamford Road, Kettering, when he was assaulted.
As he waited outside the shop, a girl left the building and fell to the floor in front of him.
While he checked if she was okay, a man got out of a nearby car and punched him.
The car was white and may have been a Honda Civic.
The assault happened at some point between 11.30pm on Saturday, March 1, and 12.30am the following morning.
Witnesses to this incident, or anyone with any information, can call Northamptonshire Police on 101 or Crimestoppers anonymously on 0800 555 111.