[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/dr_jekyll_and_sister_hyde_martine_everett.jpg]]

A 1971 Film/HammerHorror film adapting ''Literature/TheStrangeCaseOfDrJekyllAndMrHyde'' with several changes.

The dedicated Dr. Jekyll is attempting to find a cure for all disease. Realizing that this research could take longer than his natural lifespan, Jekyll derails into a search for an "elixir of life", some way of slowing the aging process. He hits upon human female hormones as a possible main ingredient, and early experiments seem to bear him out.

The problem now is that synthetic hormones don't exist yet, and no sane woman is going to volunteer to have her hormone-producing organs removed. So Jekyll turns to body snatchers Burke and Hare. Armed with his new supply, Jekyll develops his serum...but it has some [[GenderBender side effects]]. When the body snatchers are put out of business, Jekyll must find yet another supplier for fresh female hormones, while dealing with some personal issues.

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!!Trope in this film include:
* AloofDarkHairedGirl: Hyde.
* AndYourLittleDogToo: Hyde tries this towards Jekyll's love interest, in hopes of destroying his will to live.
* ArtisticLicenceHistory: Burke and Hare ply their trade right alongside Jack the Ripper.
* ArtisticLicenceBiology: Jekyll's theories of women possessing the hormones for eternal life are nonsense...but they're an [[ExcusePlot excuse]] to get the plot going.
* AttractiveBentGender: Doctor Jekyll turns into his female alter-ego- Sister Hyde- whose beauty and sexual appeal catches the eyes of several men, including Jekyll’s love interest’s brother.
* BitchInSheepsClothing: Ladies of Whitechapel think they'll be safe walking home with another woman. [[SerialKiller They are very, very wrong.]]
* TheCasanova: Professor Robertson. [[spoiler:It proves his undoing.]]
* CurtainClothing: After transforming from Jekyll into Hyde, the female Hyde pulls down some red draperies and fashions them into a dress.
* TheCutie: Susan.
* DisposableSexWorker: As per the real Whitechapel murders.
* EyeScream: The body snatcher Hare is blinded when an angry mob tosses him into a lime pit.
* FalseWidow: Hyde's cover story, allowing her to freely pursue a new husband.
* GenderBender: Doctor Jekyll to Sister Hyde.
* GothicHorror
* GrandTheftMe: The main struggle between Jekyll and Hyde.
* HangingByTheFingers: Dr. Jekyll attempts to escape from the police over the rooftops. He slips and falls and winds up hanging from the fingers from the gutters.
* HowWeGotHere: The movie opens with Jekyll's [[ApocalypticLog doomed confession.]]ky
* ImmortalityImmorality: Requires other people's body parts, and the main character starts taking them by force.
* InformedAttractiveness: Almost everyone who sees Mrs. Hyde remarks on her beauty. One character is even surprised that Jekyll could have a sister so fetching.
* UsefulNotes/JackTheRipper: [[spoiler: Jekyll himself, and later Mrs. Hyde.]]
* JekyllAndHyde: As indicated in the title.
* TheJekyllIsAJerk: While Jekyll is a WellIntentionedExtremist, ''he'' is the one who starts the killing spree, independent of Hyde.
* LadyInRed: Hyde's GorgeousPeriodDress.
* LineOfSightAlias: Jekyll explains that the woman seen in his flat the previous night (actually him transformed into a woman) was his sister. When Susan asks her name, Jekyll glances at the newspaper in his hand and sees the headline "Murder in Hyde Park", and replies:
-->"Hyde...Mrs. Hyde...She's a widow."
* LoveMakesYouEvil: Falling in love is one of the reasons Hyde is determined to have complete control of her body.
* MadScientist: Jekyll, of course.
* MadonnaWhoreComplex: Susan Spencer is a modest, sweet, virginal GirlNextDoor smitten with Jekyll. Sister Hyde is a sexually liberated exotic beauty and a SerialKiller to boot.
* ManIFeelLikeAWoman: After his first transformation into a woman, Jekyll opens his dressing gown and gazes in wonder at his breast before starting to fondle it. the moment is spoiled when the hand doing the fondling turns back to male.
* MistakenForGay: Howard believes Jekyll’s isolated lifestyle and his disinterest in Susan’s clear affection towards him are signs of doctor not being entirely “normal”. Later Jekyll (influenced by Hyde’s persona) strokes Howard’s face affectionately, which doesn’t help the case.
* MultiGenderedSplitPersonalities: The main character is a man whose [[JekyllAndHyde Hyde]] is a woman.
* RomancingTheWidow: Howard Spencer is strongly attracted to Sister Hyde, and so does she to him, much to Dr.Jekyll’s dismay.
* SiblingTriangle: Susan Spencer has a thing for Dr. Jekyll, while her brother Howard is attracted to Mrs. Hyde. Naturally, they don't know that the two are the same person
* SlowlySlippingIntoEvil: Jekyll goes from buying bodies, to buying suspiciously murdered bodies, to finding his own sources...
* WellIntentionedExtremist: Jekyll.

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