Fifteen years have passed since the enigmatic disappearance of Francesca, daughter of celebrated author Vittorio Visconti. A deranged killer is now terrorizing the city, seeking to purge it of "impure and damned souls". As the police struggle to make progress, detectives Moretti and Succo take on the case, determined to unravel the mystery behind these gruesome crimes. But when Francesca seemingly returns, it becomes clear that she is not the same innocent girl everyone remembers.