The incident happened on Saturday, November 30, between 5.20pm and 5.40pm, in Kingsley Road, when a silver Vauxhall Astra was in collision with a man in his 30s.
The car then drove off, according to police.
The man received serious injuries and a 27-year-old man has been interviewed in connection with this incident.
Anyone who witnessed it or has any information about it should call Northamptonshire Police on 101.