Police are investigating an attack on two Polish men by three English men in Boston on Saturday night.
The incident took place on the junction of Queen Street and Broadfield Street at about 11.35pm.
It is not yet clear whether the assault was racially-aggravated.
Police would like to hear from anyone who witnessed the incident or who has any information about it.
A spokesman said: “We would particularly like to hear from the man who followed the suspects and pointed them out to police. He could potentially be of great help to the investigation.”
The three men have been arrested and bailed on suspicion of assault.
Anyone with information is asked to contact PC Janette Campbell at Boston Police Station by calling 101. Alternatively call the charity Crimestoppers anonymously on 0800 555111.