In a tiny, barely-known mountain village live the ponies who once worshipped Nightmare Moon. Twilight discovers that Luna is planning to visit them, but doesn't want anypony else to know. Just what is the Princess of the Night trying to hide? The more Twilight investigates, the more her suspicions grow that an ancient and evil ritual is about to take place. There is only one way to be sure: secretly follow Luna on her journey. But, as Twilight will find out, all knowledge comes with a price...