A 1982 Italian Horror film from master horror film maker Creator/DarioArgento. It stars Anthony Franciosa, Veronica Lario, John Saxon, and Daria Nicolodi.

The film was released in Italy and through most of Europe without any reported censorship problems, but was classified and banned as a VideoNasty in the United Kingdom. Its theatrical distribution in the United States was delayed until 1984, when it was released in a heavily censored version under the title ''Unsane''.

Franciosa stars as Peter Neal, a American writer of violent mystery novels. In Italy to promote his latest work, he is accompanied by his literary agent Bullmer (Saxon) and his assistant Anne (Nicolodi). He is unaware that he is also being followed by his embittered ex-wife Jane (Veronica Lario).

Prior to Neal's arrival in Rome, a young woman is brutally slashed to death by an unseen killer. The murderer sends Neal a letter informing him that his books have inspired him to go on a killing spree. Neal is soon contacted by the police, who put Detective Giermani (Giuliano Gemma) in charge of the investigation.

While the killings continue, Neal notices that TV interviewer Christiano Berti (John Steiner) appears to have an unusually intense interest in the novelist's work.

Just when you think you know who the killer is, he is violently killed himself.

!!This film provides examples of:

* AccidentalMurder: In the end, [[spoiler:Anne accidentally kills Neal when she pushes a statue and one of its sharpest pieces pin him on the wall.]]
* AngryGuardDog: Maria is frightened by one. She then foolishly aggravates it further, providing a chase scene that leads her to the killer's basement.
* AnAxeToGrind: Primary tool for murder during the latter part of the film.
* AxCrazy: [[spoiler:Both Cristiano Berti and Peter Neal.]]
* BigBad: [[spoiler:Subverted with the reporter [[FirstDiscFinalBoss Cristiano Berti]] who indeed kills the first few victims but is killed by Peter Neal who then takes over as the BigBad]].
* BigBadWannabe: [[spoiler:Cristiano Berti, who was indeed the murderer of the first few victims, but is killed off by Peter Neal, the actual BigBad.]]
* DecoyProtagonist: [[spoiler: For initially most of the movie, the film follows Peter Neal, however, after Neal takes over as the BigBad, the climax follows [[FinalGirl Anne]] instead.]]
* FinalGirl: Anne.
* {{Gorn}}: It's Creator/DarioArgento. What do you expect?
* GreaterScopeVillain: [[spoiler:Due to the revelation that Peter Neal was the killer for the later act and his literary work (which in turns inspired FirstDiscFinalBoss Berti to go on a murder spree) stems from his DarkAndTroubledPast as a teenager who killed a girl out of revenge for the humiliation he suffered, Neal act as this for Berti in the first half of the film.]]
* ImpaledWithExtremePrejudice: Happens to the killer in the climax.
* [[spoiler:TheKillerInMe: Peter Neal has always had repressed feelings of misogyny and violence. He takes them out by writing in his books. But once somebody starts killing due to his books, he loses any control he had, kills the actual killer and embarks on a spree of his own.]]
* MetafictionalTitle: ''Tenebre'' is Neal's latest book.
* MsFanservice: The lesbian reporter Tilde's girlfriend, who is naked for almost entire duration of her role.
* TheOner: The three minute shot that pans over Tilde's house.
* TheQuincyPunk: While waiting for Jane to have lunch with her, Bullmer notices two punks hanging around.
* RealitySubtext: A feminist reporter lambastes Neal for his novels' focus on brutal violence against women, a criticism often leveled at Argento specifically and the giallo genre in general.
* RedHerring: All [[spoiler:male]] characters but particularly [[spoiler:John Saxon who plays a sleazy agent]]. Subverted with [[spoiler: Berti who is the killer but gets killed by Neal who takes over as the killer.]]
* SlashedThroat: How the first victim dies.
* TwistEnding
* VideoNasty
* [[spoiler: VillainProtagonist: Peter Neal.]]