Lincolnshire Police are looking for information on a man captured on CCTV after three assaults in the city centre.
The incidents took place on July 15, starting at around 2am on the High Street.
The suspect punched a 15-year-old boy outside KFC, knocking his to the ground. He then headed into the city centre with two friends.
Outside St Peter at Gowts Primary school, also on High Street, the same man is believed to have punched a 47-year-old woman and a 56-year-old man.
The woman lost consciousness briefly, while the man suffered a broken nose.
Police would like to speak to the man in the CCTV image in connection with the incident.
Anyone with information should contact PC Tracey Aerstall, quoting incident number 79 of July 15, on 101 or call Crimestoppers anonymously on 0800 555 111.