Things aren't going well between Celestia and Luna. As tensions grow between them, it is quite clear that they simply aren't the same ponies they once were. Instead of risking the loss of each other's companionship, both agree that perhaps some distance would help them recover a little. Besides, Celestia could use the vacation anyways.

But the beach town of Dusk Falls is hardly the peaceful and quiet abode Celestia had been expecting. Amongst the boardwalks and carousels a sinister plot is unfolding, as trouble rises both in the heart of Equestria and in Celestia's new home.

Cover-Art Celestia Vector here and the picture in the letter 'D' is here.