Glen or Glenda?

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The film begins with a narrator, called The Scientist, making cryptic comments about humanity. He first comments that humanity's constant search for the unknown, results in startling things coming to light. But most of these "new" discoveries are actually quite old, to which he refers to as "the signs of the ages". Later, the scene turns to the streets of a city, with the narrator commenting that each human has his/her own thoughts, ideas, and personality. He makes further comments on human life, while sounds accompany some comments. The cries of a newborn baby are followed by the sirens of an ambulance. One is a sign that a new life has begun, the other that a life has ended.[1] [2]
This last comment starts the narrative of the film. The life which has ended is that of a transvestite named Patrick/Patricia, who has committed suicide. A scene opens with his/her corpse in a small room. Within the room is an unidentified man who opens the door to a physician, a photographer, and the police. A suicide note explains the reasons behind the suicide. Patrick/Patricia had been arrested four times for cross-dressing in public, and had spent time in prison. Since he/she would continue wearing women's clothing, subsequent arrests and imprisonment were only a matter of time. So he/she ended his/her own life and wishes to be buried with his/her women's clothing. "Let my body rest in death forever, in the things I cannot wear in life."[1] [2]
Inspector Warren is puzzled and wants to know more about cross-dressing. So he seeks the office of Dr. Alton, who narrates for him the story of Glen/Glenda. Glen is shown studying women's clothes in a shop window. Dr. Alton points out that men's clothes are dull and restrictive, whereas women can adorn themselves with attractive and comfortable clothing.[1] [2] A flashback scene reveals that a young Glen started out by asking to wear his sister's dress for a Halloween party. And he did, despite his father's protests. But he then continued wearing his sister's clothing, and Sheila (the sister) eventually caught him in the act. She shuns him afterward.[1]
The narrative explains that Glen is a transvestite, but not a homosexual. He hides his cross-dressing from his fiancÃ©e, Barbara, fearing that she will reject him.[1] [2] She has no idea that certain of her clothes are fetish objects for him. When Barbara notices that something is bothering him, Glen does not have the courage to explain his secret to her. She voices her suspicion that there is another woman in his life, unaware that the woman is his feminine inner self, Glenda.[1] The scene shifts from a speechless Glen to footage of a stampeding herd of bison, while the Scientist calls for Glen to "Pull the string". The meaning of the call is unclear, though it could be a call for opening the proverbial curtain and revealing the truth.[1]
Alton narrates that Glen is torn between the idea of being honest with Barbara before their wedding, or waiting until after. The narrative shifts briefly from Glen's story to how society reacts to sex change operations. A conversation between two "average joes", concludes that society should be more "lenient" when it comes to people with tranvestite tendencies.[1] The story returns to Glen, who confides in a transvestite friend of his, John, whose wife left him after catching him wearing her clothes.[1]
Later, a scene opens with Glenda walking the city streets at night. He/she returns home in obvious anguish, when the sound of thunder causes him/her to collapse to the floor. The Scientist cryptically comments "Beware! Beware! Beware of the big, green dragon that sits on your doorstep! He eats little boys, puppy dog tails, and big, fat snails! Take care! Beware!"[1] This serves as the introduction to an extended dream sequence. The dream opens with Barbara anguished at seeing Glenda. Then Barbara is depicted trapped under a tree, while the room around is in a chaotic state. Glenda fails to lift the tree and rescue Barbara. Glenda is replaced by Glen, who completes the task with ease.[1] The dream then depicts Glen and Barbara getting married. The priest seems normal but the best man is a stereotypical devil, smiling ominously, suggesting that this marriage is damned.[1] The dream shifts to the Scientist, who seems to speak to the unseen dragon, asking it what it eats. The voice of a little girl provides the answers in an apparently mocking tone.[1]
The dreams continues with a strange series of vignettes. A woman is whipped by a shirtless man in a BDSM-themed vignette. Several women "flirt and partially disrobe" for an unseen audience. A woman tears apart her dress in a dramatic manner, then starts a coy striptease.[1] The whipped woman from an earlier vignette appears alone in an autoerotic session. Her pleasure is interrupted by another woman who forcibly binds and gags her.[1] Another woman has a similar autoerotic session and then falls asleep. As she sleeps, a predatory male approaches and rapes her, with the victim seeming partially willing by the end of it.[1] Throughout these vignettes, the faces of Glen and the Scientist appear. They seem to be silently reacting to the various images.[1]
The dream returns to Glen, who is haunted by sounds of mocking voices and howling winds. He is soon confronted by two spectral figures. A blackboard appears, with messages recording what the Scientist or the mocking voices said in previous scenes. A large number of spectres appear, all gazing at him with disapproval, as if serving as the jury of public opinion on his perceived deviance. The mocking voices return.[1] The Devil and the various spectres menacingly approach Glen. Then the Devil departs, Glen turns into Glenda, and the spectres retreat.[1] A victorious Glenda sees Barbara and approaches her, but she turns into a mocking Devil. Barbara starts appearing and disappearing, always evading Glenda's embrace. Then she starts mocking her lover. The Devil and spectres also shift to mocking Glenda. The dream sequence ends.[1]
Glen/Glenda wakes and stares at his/her mirror reflection. He/she decides to tell Barbara the truth. She initially reacts with distress, but ultimately decides to stay with him. She offers him/her an angora sweater as a sign of acceptance. The scene effectively concludes their story.[1]
Back in Dr. Alton's office, he starts another narrative. This one concerns another tranvestite, called Alan/Ann. He was born a boy, but his mother wanted a girl and raised him as such. His/Her father did not care either way. He/She was an outsider as a schoolboy, trying to be one of the girls and consequently rejected by schoolmates of both sexes. As a teenager, he/she self-identified as a woman. He/she was conscripted in World War II, maintaining a secret life throughout his/her military service. He/she first heard of sex change operations during the War while recovering from combat wounds in a hospital. He/she eventually did have a sex change operation, enduring the associated pains to fulfill his/her dreams. The World War II veteran becomes a "lovely young lady".[1] Following a brief epilogue, the film ends.[1]

Question: who tears apart her dress in a dramatic manner?
Answer: A woman