A reveller was left unconscious after being attacked in the street by a gang in Halloween costumes.
A 19-year-old woman also suffered nasty facial wounds when she tried to step in to defend the 21-year-old victim from attackers in fancy dress costumes.
They were approached by two men and a woman as they waited for their friends outside the Ann Summers shop on Fishergate Preston, at around 1.30am on November 1.
An argument broke out between the groups, and the 21-year-old man was punched and knocked unconscious by one of the men in a vicious attack.
As the frightened 19-year-old woman went to his aid, the woman punched her, leaving her with facial injuries.
CCTV images have been issued of a man and a woman who police want to speak to. Both victims, who were taken to the hospital for treatment, did not wish to speak about their ordeal.
But DC Justin Singleton of Preston CID said: “This is a vicious, nasty and unprovoked attack on two young people who had been enjoying a night out in the city centre.
“The woman has been left with substantial facial injuries and the man was rendered unconscious so I urge the persons responsible to come forward or anyone with any information at all to please to come forward.”
The attackers fled on foot on to Guildhall Street and were later seen walking towards Preston Railway Station.
The woman is described as white, in her late 20s, 5ft 6in tall, of skinny build with curly long blonde hair.
She wore a black leotard, black stockings and a black tutu with black knee length boots. The first man was white, in his late 20s, 6ft tall of medium build, with short dark hair.
He was wearing a black t-shirt, black skinny jeans, and had half of his face painted white. Police say they were with another man, who was white, aged in his early 30s, 6ft tall, of large build. He was wearing a white suit with pin stripes and earlier in the night it is believed he was wearing a white fedora-style hat.
“We are particularly keen to talk anyone who was near to the scene at the time of the incident who may have seen the suspects in the vicinity,” DC Singleton said.
Contact Preston Police on 101 quoting log reference 0192 of November or Crimestoppers on 0800 555111.