And they are appealing for members of the public who saw anything unusual or know anything about the incident to get in touch.
At 6.35am on Saturday May 17, a woman was working in McDermid's newsagent on the High Street, Dumbarton when a man entered the shop carrying a weapon.
He demanded money, threatened the shop worker with what police describe as a bladed weapon, but ran off empty handed.
It is not known which direction he headed in when he fled the premises.
The 60-year-old woman managed to contact the police and raise the alarm.
Detectives from Clydebank police office say the member of staff was uninjured but has been left extremely shaken as a result.
The suspect is aged between 18 and 23-years-old, white, thinly built with a local accent.
He is about 5ft 2in tall and was wearing a dark grey waterproof jacket with the hood up
The jacket had lighter coloured patches on both shoulders and a white logo on the left side.
He was wearing a football scarf covering the lower half of his face, had on dark grey coloured trousers with lighter coloured bands on the sides and was carrying a dark rucksack.
Detective constable Stevie Monaghan is heading the hunt for the would-be robber.
He said: "This was a terrifying incident for the woman concerned who was simply working in the store when she was targeted.
"I would like to appeal to the local community for information to help catch this suspect.
"At that time of day, the street may have had some people around going to pick up their morning paper.
"I would urge anyone who may have been in the vicinity to contact officers as they may have information that could assist our inquiry."
Anyone with information is asked to contact Clydebank CID on 101 or Crimestoppers on 0800 555 111.