Plot
The movie opens with a woman, Angela, shown just after sex with a man who's cowering under bedsheets and angrily harassing the woman from not being fully satisfied out of shame. When Angela gets her things, she knocks a chest over with bladed weapons, which scares her and causes her to flee. Unwittingly taking a blue scrapbook with her, she reads it and sees its memorabilia an unidentified serial killer in Turin, nicknamed "The Dwarf Killer". The unseen killer from before calls Angela and threatens her life. With the train conductor of no help, she calls her dear friend Marta to retrieve the scrapbook from her at the station. As the killer's found Angela and followed her on the train, he chases her and cuts off her finger when she tries to close a door on him or jump off the train. When she's cornered, he slashes her throat. Marta, after Angela does not meet her at the station, hops onto the train to find Angela, but she finds Angela's gold pin and the blue scrapbook behind a chair. She narrowly avoids getting stuck on the train and takes the book with her to her car. The killer follows her, barges through her car door, and stabs her to death in the driver's seat before taking the book back.
Detective Ulisse Moretti (Max von Sydow) was the primary investigator of the original series of murders in 1983, and has been keeping in close contact with Giacomo Gallo, the only survivor of the original spree who saw his mother, Maria, stabbed to death in her mouth with her own English horn. The first three killings in the spree became known as The Dwarf Murders because the main suspect, Vincenzo de Fabritiis, was a writer of crime fiction with dwarfism, but he died of natural causes and the case was considered closed. Detective Moretti, since retired from the force, was never fully convinced of Fabrittis' guilt. Giacomo has taken years to cope with the trauma of his mother's murder, despite nagging missing details haunting him since the murder. Giacomo's girlfriend, Gloria, and his best friend Lorenzo Betti have just returned from studying abroad (arranged by Betti's aristocratic father).
Meanwhile, the killings continue to escalate. Nightclub worker Mel is just getting off her shift, when the killer follows her, then jumps her in a surprise attack. Dragging her to an indoor fountain during a lengthy struggle, he drowns Mel, then aggressively cuts her fingernails very short because she scratched him during the fight. Moretti is back on the case unofficially, and Giacomo joins him, offering his memories and because he needs answers for the sake of his mother. The variations in the murders puzzle them both, as does the change of being in the same neighborhood in 1983, to spread across the whole city.
Beppe finds information on the killer and blackmails him into arranging a meeting. The killer confronts Beppe by stabbing him to death. Giacomo questions de Fabritiis' friend Leone, who also has drawfism and drinks too much. Vincent's mother Laura is highly unhappy to see Moretti and still grieving the death and slander of her son. The killer murders another woman, Dora, by pushing her into her apartment building and slamming her face into a wall repeatedly, hard enough to knock her teeth out. While conversing with his pet parrot, Moretti goes over the murders and realizes the modus operandi matches the violence in a disturbed nursery rhyme, "The Crazy Farmer". He reconvenes with Giacomo and reads the rhyme, mentioning a farmer was driven insane and killed all his animals the same way each of the victims were murdered. He theorizes the killer was mad from the nursery rhyme after hallucinating the noises of the animals, and they eventually figure out the likely next victim: since the last animal to die is a swan, they go to a ballet to try and protect the dancers. They're too late, as one, Mara, is violently beheaded by the killer.
Laura eventually sees a silhouette she assumes is Vincent, which scares her into falling over her banister in her home and she dies from the fall. Detective Moretti is scared into a fatal heart attack from the same silhouette in his home. Giacomo knows they were murdered, so he goes to Leone's apartment for evidence, only to find he has been shot in the face and has died. Betti's father appears and shoots Giacomo in his shoulder. After changing his mind about killing him, Betti's father apologizes to Lorenzo, who appeared on the scene with Gloria, and shoots himself in the head. Giacomo then realizes the killer of both sprees was not a dwarf, but a child, which explained his expanded mobility.
Giacomo confronts Lorenzo as the killer, with one crucial piece of evidence: a hissing sound he heard during Marta's murder was Lorenzo's medical inhaler. Mr. Betti transferred Lorenzo out of the country to stop him, then killed Leone when he was sure Lorenzo was murdering again. Lorenzo smugly confesses he doesn't care his father's dead, and he was glad to return for the "game" of Giacomo trying to catch him. Lorenzo was driven mad by hearing animal noises, hallucinating them coming from women and killing them accordingly based on the rhyme. They never felt in danger in 1983 because of his young age, and when he went to Geneva and New York City, he slaughtered more people since the nursery rhyme was known internationally.
When Giacomo tries to grab a kitchen knife, Lorenzo pulls his own knife on Gloria and threatens to kill her if he doesn't leave. Giacomo complies just enough for Lorenzo to get to a window, where the active detective on the case shoots Betti's shoulder, then blows a shot through his head, killing him instantly. The scene is a bloody mess, and the police raid the apartment while Giacomo consoles Gloria over the murders finally being over.
