Police believe CCTV could hold the clues to an attack in Cardiff which left a surfer seriously injured.
The 29-year-old from Bridgend suffered serious head injuries when he was assaulted outside McDonalds in St Mary Street on 11 December.
Officers have released images of people they believe may hold crucial information about the incident.
Two men aged 22 and 28 are currently on police bail, while the victim remains in hospital.
His family have described the time since the incident as a "harrowing experience" and have asked that his full name is not revealed.
The man, who is described as a "keen surfer", suffered a fractured skull in the assault.
It took place at around 2200 GMT on Saturday 11 December.
He was initially in intensive care, then the high dependency unit, but has since been moved to another ward.
Det Sgt Mark Vaughan from Cardiff Bay CID said: "Statements were taken from some individuals at the scene but having viewed CCTV footage it is apparent that there were a number of other witnesses.
"We are particularly keen to trace a man and a blonde woman, who were together outside McDonalds, and a man wearing a white T-shirt with a distinctive logo on the back, who can be seen on CCTV in St Mary Street close to where the incident took place.
"I would appeal for these people, and anyone else who was in the area, to contact us as they may have crucial information."
'Keep our streets safe'
His family have joined police in appealing for information from other witnesses who have not yet come forward.
In a statement they said: "That someone can go from a night out with friends in the city centre to being in a life-threatening condition has completely shocked us all.
"It has been a harrowing experience that has had a devastating impact on Christmas.
"He spent five days in intensive care, five days in the high dependency unit and, although he is progressing well, his treatment will continue for many months.
"As a family we are encouraged by those who have already spoken to officers but would urge others who may have witnessed the incident to contact police as soon as possible so they can help keep our streets safe."
Anyone with information is asked to contact Cardiff Bay CID on 02920 527 420 or Crimestoppers anonymously on 0800 555 111.