A man was apparently assaulted in Montagu Street, Kettering, early on Sunday, March 8.
The man received hospital treatment after being found collapsed on the pavement by police officers.
The assault is believed to have happened during an incident in Boston’s Diner in Montagu Street some time between 1.50am and 2am.
The man was taken to Kettering General Hospital for treatment. A second man is also believed to have been injured in the same incident.
Witnesses, or anyone with information, are asked to call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111.