Police are searching for a man who sexually assaulted a 21-year-old woman on deserted waste ground.
The woman, from the Rodwell area of Weymouth, Dorset, was returning home from a night out when she was grabbed.
Police believe the attacker had been following the woman before dragging her to the back of council offices in the Boot Hill area on Friday night.
Detective inspector Mick Rand said: "This was a very traumatic experience for the young woman, who was very frightened, and an unusual occurrence for Weymouth.
"It may be that someone, or perhaps several people, may have been returning home around the same time and may have seen the young woman with the male attacker, mistakenly thinking that they were a courting couple."
The victim managed to return home to alert police after the attack.
The scene of the assault has been examined by scenes-of-crime officers.
Detectives are keen to trace a man in his early 20s who was wearing a dark woollen bobble hat and gloves as well as a coat and dark trousers.