Police have issued an efit image of a man suspected of raping a 40-year-old woman on a canal towpath while two other women stood by and watched.
The attack is believed to have happened at 0040 BST on Friday
Police say the victim was attacked and possibly hit with an object before being raped in Reading, Berkshire, during the early hours of Friday.
She was sitting on the towpath under the railway bridge in George Street, Caversham, when the male attacker and the two women approached her.
After the attack, the three made off, leaving the woman sat under the bridge for around an hour, in a state of shock.
She reported the incident to police later that day and was interviewed by specially-trained police officers.
The attacker is described as black, aged 40 to 45, with his hair in braids and having a large smile, with a gap between his front teeth.
The first woman was white, blonde and aged 20 to 30 while the second was white, brunette and aged 25 to 35.
Detective Constable Mick Bland said: "The towpath where the incident is said to have happened is a busy thoroughfare to residential areas.
"I'd appeal for anyone who was walking in the area at the time, perhaps on their way home from a night out, who may have seen the man and the two women, or the victim sitting alone, to come forward as soon as possible.
"In the meantime, detectives are working with the victim in a bid to get all the information they can about this incident and move the investigation forward."