How does Mitch react to Blanche's confession?

In Scene Nine, 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.