A man was taken to hospital with a head injury after being punched in a "random and unprovoked" attack.
The assault happened just before 2.50am in Edinburgh outside the Iceland supermarket on Easter Road.
The 24-year-old victim was walking alone after a night out in the city when he was attacked.
Police said the 24-year-old man had just turned left from London Road into Easter Road when he became aware of a man and a woman walking behind him.
The male suspect then engaged the man in conversation before punching him in the head.
Paramedics from the Scottish Ambulance Service took the victim to the city's Royal Infirmary for treatment to a head injury and he was later discharged.
Officers are now appealing to anyone who may have seen the couple to come forward.
Following the attack, they headed north on Easter Road before being lost from view.
The male suspect is described as being white, around 5ft 8ins to 6ft tall and about 25 years old with short dark hair. He spoke with a Scottish accent and was possibly wearing a witch's hat along with a red hooded top and dark jeans.
The woman, believed to be around 20 years old, had been wearing a distinctive pink princess-style dress, with long curly blonde hair and was carrying her shoes.
Detective Chief Inspector Martin MacLean of Police Scotland said: "It appears that this was a random and unprovoked attack and we are carrying out various lines of inquiry in order to trace the male responsible.
"Given the distinctive dress worn by the woman who was with the male at the time, I would hope that someone remembers seeing or speaking with them at some point during the evening.
"I ask anyone with such information to contact police on 101 or, alternatively the registered charity Crimestoppers on 0800 555 111."
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