Altona North Embona Taskforce detectives are appealing for witnesses following an attempted robbery at a convenience store in Newport on 16 October.
Investigators have been told a man entered the premises on Schutt Street around 8.20pm.
The man jumped over the counter and confronted the woman attendant, punching her at least four times to the upper body.
The woman reached for a knife from under the counter and the offender fled empty handed.
He was last seen running south on Schutt Street towards Mason Street.
The offender is described as Caucasian in appearance, approximately 20-years-old, 175cm tall and with a medium build.
He was wearing a grey ‘hoodie’ jumper under a black jacket and a black peaked cap.
Investigators have released an image of a man they believe may be able to assist with their enquiries.