A teenager was knocked unconscious in an attack in Oxford.
A Good Samaritan found the 18-year-old at about 9pm in Jeune Street on Wednesday and called an ambulance.
The teenager had been carrying a white carrier bag at the time of the attack.
He discovered that his phone and wallet had been stolen in the incident.
Investigating officer Police Constable Jamie Thornton said: “Unfortunately the victim has no recollection of the incident so we need the public’s help to piece together what happened.
“Due to the time of night there is likely to have been many people around.
"The victim walked down Stockmore Street towards Cowley Road, then crossed over and went down Jeune Street.
"Anyone with any details which may assist the investigation is asked to contact officers.”