Moaning Myrtle is the ghost that haunts the girl's bathroom. Her story is this:

"I was crying in the girls' bathroom because Olive Hornsby teased me about my glasses. I thought I heard a boy come in because of his voice, so I was going to tell him to get out and when I opened the door of the stall, I saw big, yellow eyes looking at me. And that's when I died. I don't know why or how, but all I remember is staring into big, yellow eyes and then dying."

THIS JUST IN! Harry, Ron, and Hermione have found out what killed her! It is a…BEEP! A IMPORTANT ANNOUNCEMENT! YOU HAVE TO READ THE BOOK TO FIND OUT!!! Thank you, that is all.