The theme of the past affecting the present is most starkly illustrated by the character of Blanche DuBois. Blanche rocks up at her sister Stella's apartment, where Stella lives with her hulking brute of a husband, Stanley Kowalski. She wants to move into the apartment in the hope of escaping from her scandalous past. Having been run out of town after having had an affair with one of her students, Blanche desperately wants to move on with her life.
But try as she might, she can't. For one thing, Stanley won't let her. He senses straight away the danger that Blanche will come between him and Stella. And so he sets out to destroy his fragile sister-in-law. As such, Blanche cannot find the stability necessary to begin constructing a new life for herself.
She thinks that the sensitive, well-spoken Mitch is just what she needs, a haven of peace in a big old scary world in which she's never really found a place. But when she tells him the sordid details of her past, he rejects her completely, forcing Blanche to realize once more that no one, no matter how ostensibly civilized and decent, is prepared to wipe the slate clean and ignore her past transgressions. Permanently trapped in the past, Blanche has no present to speak of, and certainly not much of a future.