What is the significance of the climax in the story, "Masque of the Red Death" by Edgar Allan Poe?

In addition to the answer above, remember that Poe focused his fiction (and poetry) on the idea of a "unique and single effect." He believed that all elements in a piece should build tension (both in the story and in his audience) that was to be released at the climax, creating an emotional reacton in his reader. When the Red Death comes "like a thief in the night," a sense of dread should be palpable -- no one can evade death, and Poe wants his readers to make his readers feel the futility as deeply as his characters do.