The Chestnut Man is set in the quiet outskirts of Copenhagen, where on a blustery October morning, the police make a horrific discovery. A young woman has been brutally murdered on a playground, with one of her hands missing. Next to her lies a tiny man made of a chestnut. Ambitious young detective Naya Tulin (Danica Kurcic) and her new partner Mark Hess (Mikel Falsgaard) are assigned to investigate the case. They soon discover a mysterious piece of evidence about the Chestnut Man that links to a girl who disappeared a year earlier and was presumed dead: the daughter of politician Rosa Hartung (Eben Dörner).