Anna Lind, 16 years old, disappears in the remote town of Avechot, in the middle of the Alps. The expert investigator Vogel is called to investigate, famous for creating a wide media echo around the cases he deals with. In fact, Avechot publish newspapers and television stations, which are heavily relentless on Loris Martini, a local school professor, charming but full of debts, on which the main suspicions fall. But the truth will turn out to be more convoluted than what can be thought: initially strongly suspected, later cleared when it turns out that Vogel falsified a test, putting the professor's blood on the girl's backpack, and finally the truth: Loris has deliberately circulated the clues against him but without ever leaving concrete evidence against him, in order to appear in the eyes of Vogel as the only possible killer, which would have led the investigator to do everything, licitly and otherwise, to frame it, as done in a famous case, repeatedly mentioned in the film. And on the other hand it was activated to bring out the theory that instead the murders were of a past serial killer, known as the man of the fog.