Police are appealing for witnesses after an armed robbery at the Branston Co-op store on Friday night.
The incident happened shortly after 9pm on March 18 at the food store on Station Road.
The suspect is described as being a male wearing a balaclava, blue parka jacket and light blue jeans.
He entered the shop and threatened a female shop assistant with a knife before grabbing a bag containing takings.
He then left on foot in the direction of the Lincoln Road traffic lights, police said.
The shop assistant was shocked but had not been harmed during this incident, according to PCSO Sarah Bell.
They are asking for anyone who saw or heard anything suspicious or have any information that may help them with enquiries, to call on 101 and refer to incident 445 of 18/03/2016.
Officers are also asking to hear from anyone who saw a white van parked with its hazard lights on close to Hurston’s Accountants on the High Street Branston at about 9pm.
This is the fourth armed robbery at a Lincoln convenience store in a week.
Police are also investigating three knife-point robberies that took place in Lincoln last weekend.
The first robbery was at the Co-op on Skellingthorpe Road, then shortly later at Sainsbury’s on Carholme Road, with the third at the Co-op store on Queen Elizabeth Road.
In all three cases, a man with a balaclava and/or a hoodie was described by witnesses.
However, it is unclear at this stage whether these incidents are related.