Twilight notices the book about Nightmare Moon that she had read on the eve of the Summer Sun Celebration so long ago, and is upset by the lack of detail, so she goes to a more reliable source, Princess Celestia, and asks what really happened.

(I was kind of upset that Season 4 Episode 1 and 2 aired while I was writing this, but I finished it anyway, and here it is. Criticism welcome, this is my first fic.)