THREE men were set upon in a vicious, unprovoked attack in Huddersfield town centre, in the early hours.
But only two victims have been traced.
Police are now appealing for the third man to come forward to help their investigation.
The three men were on New Street, near the Union Bank pub, when they were attacked by a gang of five men at about 1am on Wednesday.
Two of the victims, aged 34 and 46, were taken to Huddersfield Royal Infirmary with what police described as “nasty” injuries.
Officers have spoken to them about the incident.
But the third man, described as a musician with very long hair, walked away.
Pc Jo Sharp, who is investigating, said there was no apparent motive.
She added: “It is quite apparent that the third victim would have received quite nasty injuries.
“Obviously, we are concerned for his welfare, but we need him to come forward so that we can make progress on this matter.”
Four men, aged 17 to 21, have been arrested in connection with the attack and released on bail.
The third victim, or anyone else with information, should contact Pc Sharp via 0845 6060606 or Crimestoppers, anonymously, on 0800 555111.