A clubber is fighting for his life after he mistakenly wandered into the wrong house after a night out and then fell down the stairs.
Bodybuilder Stuart Lynch, 23, entered the property in Rawtenstall, Lancashire through an unlocked door while looking for a friend's house where he was due to stay.
The householder, 24, whose girlfriend was asleep upstairs when Mr Lynch wandered in, is understood to have returned home and found the man inside.
Injuries: Bodybuilder Stuart Lynch is thought to have gone into the wrong house by mistake after a night out at Vogue nightclub in Lancashire
Mr Lynch was later admitted to Royal Salford Hospital with serious head injuries and was said to be in a serious condition.
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The 24-year-old man was detained on suspicion of GBH and questioned by police before being freed on bail.
Police are thought to be investigating the possibility that an altercation ensued when the homeowner returned to find the bodybuilder inside, ending in the reveller falling down a flight of stairs.
Scene: The house where Stuart Lynch was injured and where a householder was arrested on suspicion of inflicting GBH
Night out: The 23-year-old, who is seriously ill, had been at Vogue nightclub in Rawtenstall when he entered the wrong house through an unlocked door
One neighbour said: 'We heard he had had a good Saturday night out and been offered a place to stay in the early hours but for whatever reason he must have become disorientated and got the wrong house.
'At the time we wondered what had happened because on Sunday police were out on the street.'
Today Lancashire Police said officers wanted to trace the injured man's movements between 2.30am, when he left Vogue nightclub, in Rawtenstall and 3.30am when he arrived at the suspect's house a few streets away.
Lancashire Police, who received a phone call at 3.36am, said it was not yet clear if the injured man had slipped or been pushed.
He was treated at the scene by paramedics before being taken to the Royal Salford Hospital with head injuries where he was in a critical condition yesterday.
An investigation is under way and officers are trying to piece together what happened.
Det Insp Vinny De Curtis of Lancashire Police said: 'We are investigating the possibility that this man may have gone into the address mistakenly, thinking it was a different house.
Hurt: The clubber is in a critical condition in Royal Salford Hospital (pictured) after falling down a flight of stairs at the property
'We are trying to piece together his movements leading up to his arrival there to try and establish exactly what has happened.
'We believe that the man was in Vogue nightclub in the town up until around 2:30am and we are trying to piece together his movements between leaving the club and arriving at the house on South Street.
'He was wearing a short sleeved white T-shirt, burgundy chinos and grey shoes when he was last seen at the nightclub so if anyone was in the area between 2.30am and 3.30am and thinks they may have seen him, or someone fitting that description, then I would urge them to contact the police.'