This Christmas was supposed to be a miracle. And it turned into a nightmare. In front of Jane Rizzoli's eyes, her parents' long-term marriage is crumbling, and her friend Maura confesses to a sinful relationship with a priest. One after another, gruesome murders take place, similar to ritual sacrifices. The shocked detective Rizzoli begins her usual work - the search for the killer. The investigation leads Jane to the mysterious Mephisto Foundation, whose members are convinced that these murders are the work of a demon walking among people. What is true and what is fiction in their words?