What is the horrible revelation about Miss Emily that the story ends with? How is this related to the overall meaning of the story?

The horrible revelation occurs in the very last line of the story. When the townspeople enter a room decorated like a honeymoon suite, they find a body in the bed. This, of course, is the body of Homer Barron. However, the horror is established when they find a "long strand of iron-gray hair" in the indentation of the pillow next to Homer. Since Emily's hair did not turn gray until after Homer's disappearance, this means that Emily had slept with the body of Homer after she killed him. Ironically, the townspeople who had treated Emily with so much respect and consideration simply because she was a member of an old, respected family, had been a murderer and worse. Their whole idea of the Old South was shattered by this woman who obviously broke all the rules of which she was a symbol.