A robber entered a store and used the neck of a broken bottle to threaten a member of staff and forced them to open the tills.
The man then stole a significant amount of cash.
The suspect is described as a white man, aged 20 to 25, 5ft 9ins, of medium build, with short dark hair and a goatee beard.
He wore smart pointed shoes, smart trousers and a Nike hooded top.
The incident took place at the Tesco store in Limehurst Square at around 6.30am on Sunday, May 20.
Witnesses to this incident, or anyone with information, should call Northamptonshire Police on 101 - alternatively, information can be given anonymously to Crimestoppers on 0800 555 111.