Where did Celestia disappear to, the night of the 1,000th summer sun celebration? Why didn't Nightmare Moon simply kill the mane six? What was The Nightmare willing to do in its hatred, and The Princess willing to do for her beloved little ponies?...
What would you do if you already had everything? Or everything you wanted. Her Majesty Nightmare Moon has recently discovered there is more to life than war, intrigues and edicts. Luna is trying to be helpful. She has no choice.
Despite that everypony has forgiven her, Luna still lives with the guilt of her actions and it eventually builds up too much for her to live with. Worse, guilt is only part of it.
Celestia has a dream about Nightmare Moon, while Luna can do nothing but watch her sister's nightmare. When Celestia awakens, the two sisters talk about what they've just seen.