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''Haute Tension'' (''High Tension'', also known as ''Switchblade Romance'' in the UK) is a 2003 French {{slasher film}} directed by Creator/AlexandreAja and staring Cécile de France, Creator/{{Maiwenn}} and Philippe Nahon.

Marie (de France) and Alex (Maïwenn) are two college students and longtime friends on their way to stay at Alex's parent's house for the weekend so they can study in peace. In the night, however, an insane truck driving SerialKiller (Nahon) comes to the house and murders Alex's family. He then abducts Alex herself. Marie goes after her with the intention of rescuing her, [[TwistEnding but it turns out the killer is not who he seems]]...

The original version was rated NC-17, and some bits had to be cut for it to be rated R.

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!!This films provides examples of:

* AxCrazy: The killer is ruthless in his butcheries of everyone he comes across. [[spoiler:"He" becomes even worse after it's revealed that he and Marie are the same person.]]
* BigBad: The truck driver poses the most immediate threat to everyone in the film. [[spoiler:Subverted in that it turns out he's actually a VillainProtagonist, being Marie's split personality.]]
* BittersweetEnding: [[spoiler:Alex survives, and Marie is locked away. Unfortunately, Alex's entire family has been slaughtered by Marie, with Alex being unable to recover from that traumatic experience, and Marie gets off rather easy, despite being imprisoned.]]
* BoundAndGagged: Poor Alex is in this state for most of the film, shackled by chains and gagged with a device secured with ''a lock''.
* ButchLesbian: Downplayed with [[spoiler:Marie. Her short hair and...male split personality allude to her sexuality before her PsychoLesbian nature is revealed.]]
* ChainsawGood: Both the killer and Marie get a turn with a circular saw.
* DoubleMeaningTitle: "High Tension" can refer to "high tension wire" seen in the film as well as the highly tense events that take place.
* DreamIntro: The DramaticChaseOpening is revealed to be Marie's dream.
* {{Dubtitle}}: Lion's Gate's unrated DVD is this; made obvious by some lines from the dub showing up [[FillingTheSilence when there is no dialogue in the French version]].
%% {{Euroshlock}}
* EvilAllAlong: [[spoiler:Marie]].
* FinalGirl: Subverted, in that the protagonist [[spoiler: is ''also'' the killer, leaving both Alex and the killer alive in the end. That leaves Alex, the only survivor of the massacre, as the real Final Girl of the movie.]]
* {{Foreshadowing}}: There is a lot of this, though most are nigh impossible to register without knowing the PlotTwist... and some even then.
** Marie says "the others were alone. There are two of us." [[spoiler:This goes both ways. She could be referring to the rest of Alex's family, but there's a moment of revelation that she means both that there are ''two'' of her, and that she knows the killer had other victims.]]
** There's also the huge amount of [[spoiler:ContrivedCoincidence that inexplicably allow the supposed killer to kill everybody in his way except for Marie, who is ''somehow'' always just one step ahead of him, at times even literally hiding behind his back, yet is unable to stop the killer from killing anybody, getting to witness every murder that he commits. Though not killing her, the killer gradually even starts to play XanatosSpeedChess with Marie, tricking her into taking a gun that he previously emptied so as to give her false sense of security when she next encounters him. Truly, the killer seems to be reading Marie’s mind at times – it’s almost like they're [[TheKillerInMe the same person]].]]
* GenderNonconformingEqualsGay: [[spoiler:Marie has BoyishShortHair and is teased by her best friend, Alex, for apparently being "shy" with the opposite sex, or "scared" of them. The TomatoInTheMirror ending reveals that Marie is a PsychoLesbian who is romantically and sexually obsessed with Alex.]]
* GirlWithPsychoWeapon: During the film, Marie is depicted wielding both a wooden club wrapped in barbed wire (as shown above) and a circular saw.
* {{Gorn}}: There is a lot of blood in the film and the killings are shown in loving detail in most cases.
* GoryDiscretionShot: While Alex's parents are shown to be brutally killed on screen, the audience only sees a glimpse of gunfire when the killer shoots Alex's kid brother in a cornfield.
* HillbillyHorrors: Marie talks about country people being backwards and perverted in the beginning. The killer is a man with a truck dressed in archetypal heavy-duty farm clothes. [[spoiler:Subverted in his case, as he's Marie herself.]]
* HelplessWindowDeath: Marie and Alex both watch helplessly through the window as Alex's little brother is killed. [[spoiler:Though it's revealed to be ultimately just Alex, since Marie killed him.]]
* INeverSaidItWasPoison: [[spoiler:Seeing how there was never any mention of a serial killer up until this point, Marie practically gives herself away as the killer when she implies to Alex that previous girls had been killed.]]
* TheKillerInMe: [[spoiler:The killer is Marie's alternate personality]].
* ALoveToDismember: Near the start of the film, the killer fellates himself with a woman's severed head.
* MadnessMantra
--> ''"I won't let anyone come between us anymore, I won't let anyone come between us anymore..."''
* MasturbationMeansSexualFrustration: Marie masturbates after seeing her BestFriend Alex [[ShowerScene showering]] through the bathroom window earlier that night. Since she's listening to her Walkman during the act, this prevents her from hearing the killer get into the house until the murders are well underway. [[spoiler:And that implication is how the killer personality gets in.]]
* NoNameGiven: The killer's name is never revealed. [[spoiler:This makes sense, as being Marie's split personality, of course he wouldn't have a name at all.]]
* NotSoDifferentRemark: The killer seems to be implying this to Marie when he says of Alex "She turns you on, doesn't she? She turns me on too..." [[spoiler: Of course the killer ''is'' Marie, so...]]
* NotTheFirstVictim: The killer is revealed to have had multiple other victims before Alex and her family, keeping cut-up pictures of them in his truck. [[spoiler:Or, well, Marie does. A RewatchBonus reveals that Marie tells Alex this before the apparent killer does, in a moment of {{foreshadowing}} the twist.]]
* PsychoLesbian: [[spoiler:Marie's obsession with Alex fuels her alternate personality, who kills Alex's family to eliminate obstacles]].
* SerialKiller: The truck-driving killer might be one. He has killed at least one person before targeting Alex's family, and furthermore, is shown to keep photographs of different women by the mirror in his truck.
* SlasherMovie: A strange example, as it seems to almost turn into an action movie at around the midpoint.
* ThroughTheEyesOfMadness: [[spoiler:Practically the whole story is Marie explaining how she witnessed another man committing her own crimes.]]
* TomatoInTheMirror: [[spoiler:Marie is the killer who she perceives to be attacking and killing Alex's whole family.]]
* TwistEnding: [[spoiler:The killer is in fact Marie; the truck driver is an alternate personality whom her normal side perceives as a seperate being, à la ''Film/FightClub''. Marie had a lesbian crush on Alex, and her alternate personality murdered her family so nobody could come between them though she, believing the alternate personality to be a different person, would not have to feel any guilt.]]
* UnreliableNarrator: The primary viewpoint character is Marie, [[spoiler:who is also the killer]].
* VillainProtagonist: [[spoiler:Marie is actually the killer, with that creepy truck driver just being the man she sees committing the murders.]]
* VisualPun: [[spoiler:Both of Marie's personalities came at the same time.]]
* WhamShot: [[spoiler:Of the police watching the CCTV and seeing Marie kill the security guard.]]
* {{Yandere}}: The killer wants Alex all to themself, and is not opposed to brutally murdering her entire family to do it, and everyone that comes across afterwards. Unfortunate drivers on forest roads beware.

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