A man was slashed above the eye with a knife during a party in Great Harwood yesterday.
The 27-year-old was taken to hospital following the incident in the early hours on Dryden Grove.
Detectives said both the victim and the offender had left the house by the time they arrived at the scene.
DI Jill Johnston said the victim was found wandering the streets in shorts, a t-shirt and carrying a duvet a few hours after the attack.
She added: "The victim is known to the occupants of the house. The 27-year-old went to the address armed with a knife and ended up fighting with a male and has sustained a slash injury to the eye. He is currently in hospital being treated and we are trying to establish what happened and to find the offender who left the scene following the altercation."
Police said they are searching for a man who they want to question in connection with the incident which took place at around 2am on Monday, November 27.
Anyone with any information should call 01254 353741.