"Peccavi - I have sinned!" A young woman is found mutilated - her body has clearly been used for a satanic ritual. During the autopsy, forensic pathologist Maura Isles discovers that the severed hand must belong to another woman. Then, a colleague from Jane Rizzoli's team, who has been observing a history professor, is found dead. Her body is also marked. While Jane scrutinizes the enigmatic professor and the members of his obscure foundation "Mephisto," she encounters a wall of silence everywhere she turns, and Maura finds bloodstains at her front door.