Everypony knows that Nightmare Night is celebrated to appease the entity known as Nightmare Moon. But though none of them remember, the tradition actually predates Nightmare Moon by thousands of years. What purpose did it serve all those years ago? Who was the festival for?

These questions will soon be brought to light when somepony new comes to Ponyville under the cover of darkness. Trouble and mischeif soon follow, threatening to ruin the festival. Worse, the somepony seems to have a keen interest in some of Ponyville's inhabitants...