Brother Ludovico, a brilliant and intuitive man, is sent by the Roman ecclesiastical authorities to a small town in Calabria, Italy, to investigate the death of Monsignor Ettore, a prelate well known and respected by the community. Reports from the Curia report a sudden death, due to a devious cardiac arrest, but the circumstances of his discovery arouse suspicion and prompt the Vatican to want to shed light. Brother Ludovico, partly because of his past, is the only one who can crumble the wall of distrust that characterizes a community that is only outwardly hospitable but in reality extremely closed and hostile. He leaves the same evening. Arriving in Curinga, he immediately realizes that the premises of his assignment are more than well-founded: he immediately clashes with Don Enrico, a man of kind and affable manners, but false and authoritarian. He distinctly senses the hostility of those living inside the convent. His presence is not welcomed by the locals either; they all look at him with suspicion, keeping him at arm's length. The investigation of the monsignor's death leads to doubts among all the members of the convent. To Brother Ludovico they all seem strongly out of the box and over the top, not resembling any ecclesiastical order with which he had had contact before that moment. He is sure they are hiding something. Every person who lives in Curinga fears and strictly and faithfully respects the members and the workings of the convent, a structure that seems to reign over the community, controlling everything that happens. Ludovico, will find himself, alone against everyone, discovering that the convent holds unmentionable secrets and that trying to shed light on the truth may cost him dearly. Welcoming him will be Sister Lucia and Don Enrico, a man the Cardinal presents as closed and cold, protective of the villagers but shy with those he does not know. Friar Ludovico understands what exactly the Cardinal is asking of him: looking him in the eye, he confesses that the circumstances of the Monsignor's death are mysterious; it was probably a heart attack, but there is a need to ascertain that. Even the slightest doubt that a murderer is hiding in the town must be dispelled. The Borgo di Curinga stands on a rocky knoll overlooking the sea and extends inland, in a succession of hills and flat expanses, in which it is not uncommon to come across vestiges of ancient medieval villages. Its historic center, closely resembles a medieval village, made up of alleys, streets of steps, picturesque buildings and small low houses built of stone, divided by squares and noble palaces. The convent stands outside the town and presents a different, imposing structure. Ludovico immediately arouses the attention of the inhabitants, who are surprised to see an unfamiliar face. Without giving too much thought to prying eyes, Brother Ludovico heads toward the convent, which, as the Cardinal had told him, dominates Curinga from above. Waiting for him is Don Enrico. Frowning, in the center of the sacristy, he seems to have been waiting for him for some time. Don Enrico looks down on him, studying him, while Ludovico swaggeringly sustains his gaze. Don Enrico appears different from what he had imagined; he shows himself to be all too welcoming and friendly. But in Ludovico's eyes he does not appear convincing. Don Enrico's attitude leaves no doubt: the presence of that unexpected guest is unwelcome. Don Enrico accompanies Ludovico, giving him the opportunity to visit the convent and the places where Monsignor Hector gathered in prayer. Later Ludovico will make the acquaintance of Don Gregorio, whose affable demeanor conceals a hostility and distrust that increasingly fuels Brother Ludovico's doubts. Don Gregorio celebrates Mass, his somber, sometimes macabre sermons captivating everyone. The faithful listen to him rapt and motionless, almost spellbound. Even the mother superior, Lucia, appears completely over the top: she is winking and mischievous. Not even the younger ones, Sister Beatrice and the novice friar Camillo, look like the religious one might expect, both apparently succumbing to Don Enrico. Even the janitor Saro, a shy, brusque, serious, and frightening-looking man, spends hours in his mansion and wanders the convent gardens at night. Ludovico tries to find out what really happened to the Monsignor and whether it was a natural death. Camillo, a novice friar, understanding the reasons for the presentation of Brother Ludovico proves to be the most willing to dialogue: the Monsignor, in fact, was the one who had welcomed him into the convent during a dark period of his life. Sister Beatrice, who always appears very frightened, also seems to want to say something: her eyes cry out for help but, every time Brother Ludovico tries to speak to her, the girl turns away terrified. Brother Ludovico is led to believe that Sister Beatrice cannot speak, that she is mute; since arriving at the convent after a terrible family tragedy, she has never uttered a single word. Sister Lucia recounts that Sister Beatrice had a very good relationship with the Monsignor and that his death deeply shook her, causing her to fall back into her world of silence. One night, from the window of his room, Brother Ludovico distinctly hears muffled screams and the desperate weeping of a woman coming from inside the convent. The next day, no one will admit to hearing those cries. In the following days, the chance discovery of a bottle containing an extract of stramonium, a powerful poison known as devil's herb, will set Ludovico on the right track and soon lead him to discover that Monsignor Hector has been murdered. The wall of omertà that reigns within the convent collapses in the face of this discovery: the person responsible for this terrible crime is arrested. However, there is something extremely unusual about this whole affair: the clues, the confessions, the convent itself. Despite his doubts, Ludovico decides to return to Rome. On the way to the station he is met by Sister Beatrice who, amid tears, unexpectedly implores him not to leave, saying "everything they made her believe is false!" ... "since she has been here have you ever heard of Yuria ... the missing Sister?"