Two worlds are about to collide: Patience Evans (Ella Maisy Purvis), a young autistic woman, works in a clerical role, in the basement of the City of York police station, filing investigation records. She is an enigma; a profoundly intelligent, self-taught criminologist, able to spot clues that others simply do not see. Yet her talents go unnoticed. A chance meeting with Detective Inspector Bea Metcalf (Laura Fraser) opens a door into a whole new world for her. Bea can see potential in Patience and her innate deductive skills, as well as the similarities she shares with her own son Alfie. Together, Bea and Patience form an unlikely but brilliant team for solving the most complex of murders committed within the historic city of York.