When teenager Silas is found dead at a farmhouse on the Bjäre peninsula – the perpetually angry, odd but highly intelligent investigator Dani (Krista Kosonen) is teamed up with newly graduated police colleague Malik (Mohammed Nour Oklah) to investigate the case. The investigation leads Dani and Malik into a patriarchal rat-hole on the Scanian countryside and they soon find themselves at the center of a dark family feud that has been going on for generations. Dani, who has a personal connection to the victim Silas, is drawn deep into the investigation and the families it centers around. The Patriarch Elis (Peter Gantman) gives Dani a deadline to solve the case before taking matters into his own hands within the family. Synden is a modern crime set in an uncertain world of conflict and violence where the original sin is constantly present.