In the end of the 1947 play A Streetcar Named Desire, written by Tennessee Williams, and 1951 film, directed by Elia Kazan, Blanche Dubois (Vivien Leigh) is sent to a mental institute by her sister, Stella (Kim Hunter). As her sister is being taken away, Stella questions her decision in sending her sister away. This is a typical reaction from a sister; but I believe that Stanley Kowalski, Stella's husband (Marlon Brando), made the decision that Blanche should be taken to the mental institute.
Stanley disliked Blanche from the moment that she arrived at the house, when he found out that the estate was gone. His dislike for her intensified when he overheard her telling Stella that she had married an animal. He did not want Blanche to influence Stella into their old frivolous ways and possibly leave him. Once he started learning about Blanche and her past at her home, he did not want her involved with his friend, Harold Mitchell (Mitch) (Karl Malden), either. He knew that she was a liar and that she was trying to get as much money and free living out of them as she could.
In the film, Blanche seems much more edgy and confused than in the play. She seems like more of a crazy victim than a conniving woman, like in the play. Stanley also seems much more attracted to Blanche in the film. He is often trying to get up close to her and make her look at him, but he still wants her either out of his house or as another maid, like Stella.
It was not until the night of his son's birth that he finally found out the truth of Blanche's condition. He then pushed her to her final breaking point by raping her. He also confronted her about being a liar and using men. He even bought her a bus ticket home, and then she finally left all reality behind. Stella knew that Blanche could not be by herself, especially back at home, and Stanley did not want her in the house with his new family. Mental institutions in the mid-1900s were not safe or proper places, but Stanley is so unsympathetic that he does not care what might lie ahead for Blanche. The mental institute was obviously Stanley's decision, but Stella really had no better suggestion or option for her disturbed sister. It was a tough decision, but Stanley may have helped Stella do something that she could not have done on her own.
Unfortunately, Stella is now left with a dangerous man. In the play, she stays with him by convincing herself that Blanche's story about Stanley raping her was false. In the film, however, Stella wises-up and runs upstairs with her child, claiming that she will never return to Stanley.