A teenage girl was apparently followed to her school bus stop, and then again on the way home later the same day.
The incidents happened in Long Buckby on Thursday December 8.
Northamptonshire Police say that between 7.45am and 8am, when the 13-year-old girl was on her way to school, a man followed her from near her home towards the bus stop in Station Road.
When she returned from school at about 3.45pm, the girl saw who she believed to be the same man in a small white van. He followed her for a short distance before driving off.
The man is described as white, between 25 and 35, with a slim build. He had black hair, with a fringe, and was wearing a beanie hat, zip-up black jumper and dark trousers.
Police are appealing for witnesses and anyone who may have seen anything suspicious in the area on Thursday or at any other time, is ask to contact Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111.