Police have released CCTV pictures of a man they want to talk to in connection with a robbery at the Great Park Stores in Wellingborough.
The robbery took place at around 9.30pm last Friday.
The man threatened the shopkeeper with a knife and demanded cash from the till.
He is described as white, aged 20-30, 6ft tall and of medium build. He spoke with a local accent.
Anyone with information should call Northamptonshire Police on 101 - alternatively, information can be given anonymously to Crimestoppers on 0800 555 111.