A 38-year-old man received serious injuries to his face and chest after an alleged assault on Lincoln High Street.
The assault happened at around 4.30am on the morning on Saturday, July 20.
Three Lincoln men have been charged with causing grievous bodily harm and remanded in custody.
They are Mark Guest, 36, of Monks Road, Adrian Johnson, 33, of Friars Lane and Craig Aaron Reed, 25, of Winn Street.
Lincolnshire Police have released CCTV images of a good samaritan they are urgently trying to find after she stopped to assist the injured man at the scene of the assault.
Police said: “The woman is not a suspect but could have witnessed something that might be important to our investigation.
“If you know her, please urge her to call us on 101 with incident reference 63 of July 20.”