On the German-Austrian border, bodies are found on a mountain pass. The German investigating authorities are sending young full-time commissioner Ellie Stocker from Traunstein, for whom this is the first big challenge in her career. But her Austrian counterpart, the cynical and not-so-loyal Inspector Gedeon Winter, initially has little interest in cooperating. Once further symbolic arrangements of bodies are found, it becomes clear that this is a serial criminal. Along with his victims, he leaves a message. Red Season comes and stereotypes himself as Krampus, who must punish society for their sins. The pressure on Stocker and Winter to stop the criminal increases. In their investigation, the two investigators delve deep into the dark valley, the ancient customs of the region and the delusional world of the killer.