Sunset Shimmer from the human world was adopted by the Sparkle family, and became Princess Celestia's student with her sister, Twilight Sparkle. But now, the two are sent to Ponyville to make some friends on the eve of the Summer Sun Celebration, and the fifth anniversary of when the two sisters met.

But, they are both concerned with Equestria's future, and the return of Nightmare Moon. How are they to stop this darkness when nopony believes them? Will the other ponies of this town help? What good will making friends do? And what are the Elements of Harmony? And if they can defeat the Mare in the Moon, what next?