Police are appealing for witnesses following a fight in Spalding on Saturday night.
The incident happened at about 9pm near to the hairdressers in The Crescent.
Police believe that a 37-year-old man was assaulted by another man.
The 37-year-old was taken to hospital the next day with a head injury and officers are trying to establish if his injuries are linked to the assault.
Police are particularly keen to speak to a tall, white man, of a muscular build, with short curly hair and in his mid 40s. He was with a small, thin woman, with long dark hair, also in her mid 40s.
Anyone with information should contact Lincolnshire Police on 101 and quote incident number 212 of January 6.