In the opening scene of Episode 1 of "The Monster of Florence," set in 1982, a young couple finds themselves engaged in a passionate encounter in the backseat of their car, parked on the side of a bustling highway. As their moment of intimacy nears its end, they are suddenly confronted by a man walking towards them. In a desperate attempt to flee, they try to drive away, but the man fires, striking both of them.
Cars swiftly pull up, and the sirens of the approaching police sirens echo through the night. Medics arrive on the scene and discover that the boy is still alive, while the girl is declared dead. The boy is rushed to the hospital as the police commence their investigation. Detective Silvia, with her keen instincts, concludes that the murder is specifically targeted at women, and later hands over the victim's body to her parents with a heavy heart.
Detective Vincenzo informs Silvia that the boy has also passed away, prompting her to adopt a bold strategy. She decides to "bluff" about the case, claiming that the boy has revealed crucial details about the murderer before his demise. Her bold claim that the "monster" has been described by the boy sparks a media frenzy, fueling public interest and speculation.
That night, Silvia returns to the station, her mind racing with thoughts of the eight murders of four couples that have occurred over the past few years. She explains to her partner that all the killings share a similar modus operandi, indicating a single killer targeting young couples with a pistol and mutilating the female victims.
As she reflects on the first murder that occurred in 1974, followed by a seven-year hiatus, Silvia suggests that there may have been other unlinked crimes during that period committed by the same monster. Determined to uncover the truth, she resolves to review murder cases from the past 10 to 20 years in search of connections to this elusive monster.
A few days later, Silvia and her partner uncover evidence linking the monster to another double homicide. They rush to discuss their findings with the chief of police. However, the detective reminds them that the Locci–Lo Bianco murders were committed by Stefano Mele, who killed his wife and her lover in a fit of passion. Despite this setback, Silvia remains determined to uncover the truth behind this monster and bring him to justice.
The chief, with a hunch that the monster might have used Stefano's gun to continue its killing spree, grants Silvia the permission to revisit the case. Stefano, initially, is resistant to meeting with the detectives, but flashbacks unravel a tale of coercion and a life-altering decision.
Years ago, Stefano finds himself forced into a marriage with a woman named Barbara. After losing his job, he rents a room in his home to a man named Salvatore, who eventually crosses the line and forces himself on Barbara. In a state of helplessness, Stefano allows it. Later, Barbara informs him that she is pregnant with Salvatore's child.
As the scene shifts back to the present, Stefano finally relents and agrees to speak with the detectives. They reveal that the same weapon he once owned was used to claim six other lives—three couples. Stefano insists that he threw the gun into a ditch and has nothing to do with the subsequent crimes.
When asked about Barbara, Stefano recalls bringing home Salvatore's brother, Francesco, who shocks Barbara. Stefano explains that Barbara was having an affair with Francesco, and how his own family ridiculed him for not doing anything about it. He remembers a fateful night when Barbara took their son, Natalino, to the movies with her lover, Lo Bianco. In another flashback, we see Barbara and Lo Bianco making love in a car while Natalino sleeps. Suddenly, someone shoots them, and both are killed. Natalino wakes up to find his mother dead, flees the car, and walks to a nearby house seeking help. He is later taken to the police station, where Stefano is summoned for questioning. Stefano panics upon seeing Francesco there.
At home, Stefano's family pressures him to take the blame for Natalino's sake. Stefano confesses to killing Barbara and Lo Bianco, though the detectives find it hard to believe. He insists he acted alone and threw his gun into a ditch, though the police never find it.
Stefano is eventually arrested for the murders of Barbara and Lo Bianco. Natalino later confirms that it was Stefano who took him to a stranger's house for help. In the present day, Stefano requests to see his now-grown son whom he hasn't met in years. When they finally meet, the detectives urge Stefano to tell the truth. He reveals that it was Francesco who killed Barbara for leaving him and that he confessed only to protect Natalino.
The episode ends on the night of the most recent murder, as Francesco returns home and listens to a news broadcast revealing a key detail about the killer. The narrative takes on an air of unsettling inevitability, leaving the audience on the edge of their seats as they await the next twist in this chilling tale of love, betrayal, and murder.
