A young man was knocked unconscious and seriously injured during an assault in Derry.
The alleged assault occurred at around 2.15am on Sunday at the junction between Chamberlain Street and William Street.
A spokesperson for the PSNI said: "Someone needs to be brought to justice for this.
"If you were in the area at the time and witnessed this or know who our suspect is please get in touch by ringing 101 and quoting reference number 235 of 30/07/17.
"Alternatively you can ring Crimestoppers anonymously on 0800 555 111."