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A 1992 thriller from Creator/BrianDePalma. The film stars Creator/JohnLithgow, Creator/LolitaDavidovich and Creator/StevenBauer.

The film follows Carter, who was once part of his father's cruel research, which left him with several [[SplitPersonality split personalities]]. Now as a husband and father himself, he is drawn by his other personalities to restart these experiments.

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!!This film has the examples of:

* AllJustADream / OrWasItADream / DreamWithinADream: Brought almost to the point of parody and (temporary) MindScrew, in a prolonged sequence--so that when [[spoiler: Jenny actually DOES get attacked by her husband ''just after she wakes up'', one can be forgiven for briefly being ''absolutely sure'' she's still dreaming!]]
* CatapultNightmare: Jenny gets one.
* {{Deconstruction}}: Creator/QuentinTarantino has called this film De Palma's effective deconstruction of ''[[TakeThatMe De Palma's own cinematic style]]''. [[WordOfGod De Palma himself confirmed this.]]
* DecoyProtagonist: [[ZigZaggedTrope Zig-zagged]] in a way that combines with MoodWhiplash. The film opens by following [[VillainProtagonist Carter (and Cain)]], and then switches gears to follow Jenny and her complicated love life (and dream life), coming across as an erotic thriller. And ''then'' it switches gears right back to Carter/Cain, once [[spoiler: he attacks Jenny, then switches gear back to her in the climax of the film after Carter/Cain escape from custody to meet with his still-living father]].
* FakeOutMakeOut: After drugging Karen, Carter is in danger of getting seen by two passing joggers. Cain advises him to do this to avoid their attention.
* {{Fanservice}}: Jenny provides quite a lot of this in the first half of the film, with her many makeout/come-on sequences. It helps that she has ''quite'' the ImmodestOrgasm.
* {{Flatline}}: Jack's wife flatlines when she sees him kissing Jenny in the flashback.
* GainaxEnding: [[spoiler: The final shot is of Carter-as-Margot looming behind Jenny and Amy, his/"her" intentions towards them unknown. The way it's shot (and considering a prior sequence involving something similar), we aren't even sure if he/"she" is really there.]]
* GoodSmokingEvilSmoking: Cain favours smoking.
* IdenticalGrandson: Dr. Nix Sr, and Carter and Cain. [[spoiler: And it's not because Nix Sr is another one of Carter's personalities.]]
* MamaBear:
** Jenny becomes this in the second half of the film when [[spoiler: Cain abducted her daughter Amy]].
** [[spoiler:According to Josh, Margo, [[MultiGenderedSplitPersonalities Carter's only female persona]], was the one who called the authority on Nix Sr.'s abuse toward Carter. She later backstabs Nix Sr. which completely foils his last escape.]]
* MasterOfUnlocking: Cain developed this skill when Dr. Nix was doing his research on Carter in the past.
-->Hickory dickory dock. Cain has picked his lock.
* MetafictionalTitle: The title is based on the book that Dr. Nix wrote with Dr. Waldheim.
* MultiGenderedSplitPersonalities: Carter has several split personalities, who are leftovers from the research he went through as a child. One of them is a quiet, intimidating woman named Margo, [[spoiler:who takes over to make him escape the police, and go after the real villain of the story]].
* NameOfCain: Cain, who is the most amoral of Carter's personalities.
* NeverFoundTheBody: [[spoiler:Dr. Nix's body was never found after his apparent suicide]].
* NiceJobFixingItVillain: [[spoiler:While taking his last breath, Dr. Nix accidentally shoots the spike that was in danger of impaling Jack as he tries to catch falling Amy]].
* NotQuiteDead: After being suffocated with a pillow by Cain, [[spoiler: Jenny]] wakes up in the trunk of her car just when it's going underwater. We're then led to believe that [[spoiler: she is KilledOffForReal as the car's swallowed by the river...but ''then'', we discover the body the cops found was not her--and then she makes a shocking return to get answers.]]
* TheOner: The four minute shot of Sgt. Cally and Lt. Terri escorting Dr. Waldheim to the morgue in the police station.
* TheQuietOne: Margo is the only split personality of Carter who doesn't say anything onscreen.
** Can be averted however, when Carter/Cain imagines one of his split personalities Josh to speak to him in a woman's voice, it can be likely Margo was speaking through Josh or Margo and Josh combined in Carter's psyche based on what he's thinking.
* TheReveal:
** [[spoiler:Carter's father Dr. Nix isn't another split personality of him, and he has been FakingTheDead and is pulling the strings]].
** [[spoiler:Jenny is ''still not dead'', even after we saw her go down with the car!]]
* ShoutOut: The ending shot with [[spoiler: Jenny bending down only to reveal Margo behind her]] is a direct reference to a similar shot in the climax of Creator/DarioArgento 's {{Film/Tenebre}}.
* SinisterShades: Cain sports these whenever he talks to Carter.
* SplitPersonalityTakeover: [[spoiler:Margo takes over Carter, and if the ending is to be believed, stays in control]].
* SubvertedTrope: Put it this way: If you're pretty GenreSavvy about the tropes of De Palma's previous thrillers (and the Creator/AlfredHitchcock thrillers De Palma's famous for paying homage to)...you are ''really'' in for a MindScrew!
* TrappedInASinkingCar: Cain watches his victim wake up and then start to sink into the river in a locked car.
* UseYourHead: When Dr. Waldheim tries to talk to Carter's split personality Margo, she headbutts her as part of his/her escape.
* VerbingNouny
* VillainProtagonist: Carter/Cain would qualify.
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