What is the climax of the story.

Yes, the climax comes when Roderick and the narrator realize that they've buried her alive and when she falls onto Roderick.

Then Madeline dies, and everything changes. Even when the Narrator and Usher bury her in the vault, the Narrator notes "the mockery of a faint blush upon the bosom and the face, and that suspiciously lingering smile upon the lip which is so terrible in death." It is almost as if Madeline were already mocking death (or is in some way still alive), and as though she is already mocking her brother and his friend. It would be possible to say that she does have the last laugh, breaking free from the vault and killing the raving Roderick--if this irony were not so harrowing and tragic.

What is particularly intriguing about this grotesque resurrection is that Poe finally attributes lifelike characteristics to Madeline: "There was blood upon her white robes, and the evidence of some bitter struggle upon every portion of her emaciated frame." Compare this sentence to the first description of the diseased woman as seen by the Narrator: "The lady Madeline ... passed slowly through a remote portion of the apartment, and, without having noticed my presence, disappeared." Poe's narrative choices are worth analysis, and it is telling that he writes "disappeared" without suggesting any additional movement. She was introduced with a sudden vanishing like a ghost, and she is never seen "alive" until she reappears after her burial--unless she is now a real, embodied ghost.

Tracing the progress of Madeline through the story, one quickly notes that in life she is akin to a floating waif, already a kind of apparition, while once escaped from the grave she lets out "a low, moaning cry" and falls "heavily inward" upon her brother, killing him instantly. Death gives her a strength that life did not. Likewise, the noises that continually accompany the Narrator's reading of the "Mad Trist" are essentially the first sounds Madeline ever makes in the narrative--suggesting that she has had to struggle mightily to get out of the vault. It is as if, imbued with the force of motion and the ability to produce sound, Madeline becomes "alive" only after she was buried in the vault.

3 description of setting at the beginning of the story and within the house