While pet-sitting for Princess Celestia, Fluttershy is tricked into letting a monster most vile escape from Tartarus. Soon afterwards, a curse befalls the Princess of the Night, making her unable to yield for the sun. Rumors quickly spread of Nightmare Moon's return, and that Discord is responsible. To make matters worse, Discord finds that his chaos magic cannot fix the problem, at least not permanently. Despite his efforts, the curse continues to return.

Fearing that this is the work of her greatest mistake as Nightmare Moon, Princess Luna embarks on a quest to discover the truth, set things right, and clear her name. But she will not be traveling alone. Overcome with curiosity himself, the Master of Chaos accompanies her (much to her chagrin), along with the Element of Kindness, a grumpy bunny, and a mischievous phoenix. Many perils will be faced, and many dark secrets will be revealed. But at least with Discord around, the trip will be anything but boring.

Part III of the Orthrus Trilogy.