A 25-year-old man was threatened with a knife in Dunstable town centre.
The incident took place at around 10.25pm on Saturday, February 8 as the victim was walking along Court Drive towards Asda.
He was approached by a man who asked for the time.
When the victim replied, the man pulled a small black knife from his jacket pocket and threatened him with an assault before running off towards the Gary Cooper pub.
He was a black man, in his late teens or early 20s, around 5ft 10ins tall, slim and wearing a red woolly hat, a red coat and black tracksuit bottoms with a red strip running down them.
PC Natasha Moxon-Booth is keen to speak with anyone who may have witnessed the incident or may have further information about the offender.
Contact her, in confidence, on the non-emergency number 101, or text information to 07786 200011.
Alternatively contact independent charity Crimestoppers, anonymously, on 0800 555 111, or online at crimestoppers-uk.org.