Andrea Bild, a former teacher and a heavy drinker, begins his journey through a dark and unsettling series of events that start with a seemingly ordinary New Year’s party. At this gathering, he encounters old friends and acquaintances, each of whom carries their own secrets and burdens. Among the guests is John Lubbock, a fellow teacher who has recently survived a brutal attack. John’s attack is foreshadowed by a mysterious and threatening phone call, which sets the tone for the ominous chain of events that follow.
The party also includes Edouard Vermont, another teacher who proposes to Isabel Lancia, a romantic development that deeply affects John, as he harbors feelings for her. There is also Riccardo and Sofia Bini and Silvia Monti, who play the role of a doctor and his wife, with Sofia appearing increasingly isolated due to her physical disability. Helene, a woman with a complicated past involving Andrea, was once romantically involved with him but drifted apart because of his alcoholism and other unresolved issues. The gathering seems lively, but underlying tensions, secrets, and unspoken feelings threaten to surface.
As Andrea walks home alone after the party, he is unexpectedly attacked in a tunnel, nearly murdered by an unseen assailant. Fortunately, Walter Auer and Giulia Soavi come to his aid, though the attacker’s identity remains hidden. Walter’s brief glimpse of the attacker does little to ease the suspicion and fear swirling around the group. The next morning, Andrea, now sober, learns about John’s assault from Pamela Tiffin, a reporter and John’s friend. Andrea tries to find out more but is hindered by hospital restrictions and the disinterest of Giulia, who refuses to cooperate, warning Andrea to stay out of it to avoid trouble.
Desperate to uncover the truth, Andrea visits Helene for information about John, learning from her about John's suspicious feelings for Isabel, which could act as a motive for his attack. Meanwhile, John is shown being escorted by Dr. Richard Bini, who checks in on Sofia at her home. Sofia's worsening condition becomes more menacing when a record outside her room suddenly blares loudly, guiding her to investigate. She crawls over to her wheelchair and moves toward the stairs, only to be grabbed from behind, strangled, and thrown down them—marking her as the second victim.
Andrea pieces together that there might be a connection between John’s attack and Sofia’s murder. He considers the possibility that the attacker might be targeting those connected to John, and he starts to identify potential suspects. He recalls that only a handful of people, including Helene, Edouard, Isabel, and Richard, knew John’s whereabouts that night. When a detective confirms that Richard was visiting his friend Edouard at the time of Sofia’s murder, suspicion grows. This is reinforced when a glove matching those found at the crime scenes appears, and further examination suggests that the killer might have more victims planned.
Andrea confronts Richard, who reveals that they received a mysterious phone call just before Sofia’s death, but he cannot determine if it was a man or a woman. Andrea’s suspicions deepen when he follows Richard, catching him paying a large sum of money to Walter—who is later revealed to be involved in racing and not a lover, as initially suspected. Andrea later learns that Walter is actually Luciano Bartoli’s brother, and their relationship is strictly familial.
The investigation intensifies as Andrea visits John, who is back teaching but still wearing a neck brace from his attack. During their conversation, Andrea learns that John also received strange phone calls, this time with no one speaking on the other end. Later, Andrea receives a threatening call warning him to stop poking around. Tensions escalate when Andrea is fired from his job, increasing his worry that the killer might strike again.
Attention is drawn to Edouard and Isabel, who are involved in a clandestine and illegal act—underage sexual encounters—linked to Walter. Andrea suspects that Richard might have been paying Walter to silence him and that these illicit activities may have a role in the murders. When Andrea visits Isabel at her apartment, he finds her murdered in her bathroom, with the same kind of glove, only with two fingers, floating in her bathtub.
As chaos unfolds, John announces his resignation and plans to leave Italy for Australia, overwhelmed by the violence and betrayal he has experienced. His departure is marred by a tragic discovery: Giulia Soavi has been prostituting herself at a nearby lake and is later found murdered, her throat slit. In a desperate attempt to solve the case, Andrea confronts Walter, who reveals that the attacker in the tunnel was actually Giulia’s father, mistakenly attacking John in an act of mistaken identity.
The truth begins to unravel when Andrea uncovers that every murder had occurred on a Tuesday, which aligns with Giulia’s father’s work schedule. However, the case takes a shocking turn when Andrea learns that John’s neck brace had been removed weeks ago—meaning John could not have been the attacker. As the investigation reaches its climax, Andrea finds himself at a construction site where he confronts the killer—who turns out to be John Lubbock himself.
In a tense confrontation, Andrea discovers that John’s real motive was not random violence but jealousy over Edouard’s relationship with Isabel. John had killed Isabel to be with Edouard, and he staged the murders to make it look like a psychopath was behind the killings. The final revelation reveals that John, despite being the perpetrator, was driven by a complex mixture of love, envy, and desperation. John is ultimately arrested and sent to jail, bringing an end to the deadly series of events that haunted their circle.
