A while later, Mitch arrives. They have both been drinking, and he is upset. Blanche babbles, trying to pretend this was just a normal broken date. She hears the Varsouviana playing in her head, and draws attention to the fact that the music stops after the gunshot. She avoids Mitch's attempts to get to the point, offering him a drink which he refuses on the grounds of it being Stan's liquor.
Mitch states that he has never seen Blanche in the light, that she has only ever gone out with him at night, in dimly lighted places. He tears the paper lantern off the lightbulb and stares at her in the electric light. She cries that she doesn't want realism, but magic. Mitch turns out the light and says, bitterly, that he doesn't mind her being older than he thought but he can't abide with the truth of her spotted past.
Something in her breaks at the accusations, and she admits wildly to "intimacies with strangers," which seemed to be all she was able to fill her empty heart with after Allan's death. But she'd hoped that Mitch could save her from that life. He is upset that she lied to him, and she claims that she never lied in her heart.
A Mexican woman passes outside, selling "flores para los muertos." This cracks something in her, and she begins remembering the death that brought that desire, the blood-stained sheets and the closeness of death in Belle Reve and the soldiers from the army camp who would call to her at night.
Mitch tries to embrace Blanche, to get what he'd been missing all summer. She asks him to marry her in that case, but he refuses, saying she isn't clean enough to bring in the house with his mother. She tells him to leave, before she starts shouting fire. He stares at her dumbly and she cries "Fire! Fire!" and he runs off.
Scene 9 introduces the more fantastic elements that will heighten the reality of the remainder of the play. As Blanche becomes divorced from reality, so too does the play itself become more figurative and stagey, wearing its theatrical conventions on its sleeve. Here we have the cries of the flower seller intermingling with Blanche's memories - later it will be the lighting and sound of the rape scene, and the menacing shadows of the finale.
Scene 9 is also Blanche's last attempt at recovering her aristocratic role. The jig is up, and she knows it. But when Mitch arrives she valiantly puts on her game face and resumes her flirtatious manner. Mitch is having none of it, though – he now knows that she is wearing a mask, and he wants to see what's underneath. The moment when Mitch tears the paper lantern off the lightbulb is a shocking violation, and it mirrors the rape in the succeeding scene. He has penetrated her illusion, forcing his way into the inner sanctuary of her game. It is a harsh act, and Blanche stumbles from it as if struck. Her magic has flown away, and she is left only with hated realism.
But this light of truth is, notably, not drawn from the sun but from an electric bulb – artifice exposing artifice, like throwing a white light on a painted set. She hasn't so much been exposed to reality as to stricter scrutiny, under the terms of a different sort of artifice. But it's enough to break Blanche, and the light melts the last shreds of her façade. From there, she speaks freely, if not quite sanely, of her checkered past and the devastation she has experienced.
Her lies and pretenses, till this point, have all been for an audience. She lost Stella and Stanley in the previous scene, and now Mitch, her last audience member, has stopped watching. But the fantasies are stronger than the performer, and without any outside outlet for her games, Blanche now turns the fantasies inward. She begins to deceive herself just as she tried to deceive others, and in the process becomes less and less sane.
Like Stanley, Mitch is only comfortable when he's on the offensive – when Blanche's admission begins, he doesn't know how to respond. Her speech becomes more and more unhinged as it mingles with the cries of the Mexican woman, and Mitch just falls back and listens dumbly. When she has exhausted her story of death and despair, Mitch cannot begin to process what he just heard. Instead, he fumblingly attempts to embrace her, sticking with the "she lied to me, she's just a tramp" line that he came in with, unable to deviate from that script. Blanche is even more alone than before – she bared her soul and her words fell on uncomprehending ears. The light was supposed to allow Mitch to see her for the first time, but instead it blinded him and burned her up. No wonder she screams fire.