Two women were threatened by a man who got into the back of their car at night and demanded money.
The women, aged 26 and 31, finished their shift at Scotmid Store in Riddell Street, Clydebank, at about 10pm on Sunday.
They made their way to a blue Ford Focus which was parked in front of the premises.
Before they drove off, a stranger dressed in dark clothing got into the back of the car.
He threatened them and demanded money and other personal belongings.
The women refused and told him to get out of the car, and the stranger made off.
Detective Sergeant Stuart Gillies from Clydebank CID said: “Thankfully the women were not harmed during the incident and officers are currently examining CCTV and conducting door to door inquiries in order to trace the suspect.
“We believe he may have been lurking around outside the store prior to the incident taking place and I would appeal to anyone who noticed a man acting suspiciously to please get in touch.”
Officers urged anyone with information to contact Clydebank CID via 101, quoting incident number 3654 of December 24, or anonymously through Crimestoppers.