A 33-year-old man was assaulted on a Lincoln village road, and police are looking to speak to a female driver who stopped to intervene.
Two men, aged 23 and 48, have been arrested on suspicion of assault, and have been bailed pending further enquiries.
The man was crossing Church Lane in Harmston village between 5.30pm to 5.45pm on December 3 when a red flatbed transit van stopped sharply next to him.
The male driver and male passenger got out of the van and the two men assaulted the victim.
Police are particularly keen to trace and talk to a female driver who, when passing by, stopped her car and intervened. She may be able to assist the enquiry.
The victim was not seriously injured in the incident but suffered swelling and bruising as a result.
Anyone with information relating to the incident should contact Lincolnshire Police on 101, quoting incident 283 of December 3.
Alternatively, people can contact the independent charity Crimestoppers anonymously on 0800 555 111.