CCTV images have been released of a man wanted by Northamptonshire Police for a sexual assault.
The man followed two 14-year-old girls through the covered walkway over the A45 from the Weston Favell Shopping Centre at about 1400 BST on 8 May.
He then asked both girls for sex, in exchange for supermarket vouchers and touched one of them, police said.
He is Asian, aged 30-35, slim and about 5ft 9in (1.75m) tall and was wearing a black polo shirt.
He was also wearing camouflage trousers.
Anyone who witnessed the incident or who has any other information is asked to contact police.