There's a list of secrets that the Slayer used keep from herself. Things pushed to the back of her mind. It started with where she spent the summer after burning down the gym. The Watcher used to think that too many people knew she was the Slayer. This was the secret the Slayer most wanted to keep from Buffy. Sometimes in the daylight she succeeded but the dark doesn't offer a candle a place to hide. Her dreams whispered to her who she was and in the graveyards she made sharp confessions to the dead punctuated by showers of dust.
