After a magical fire engulfs the Golden Oak Library, Twilight is transported to the Realm of the Dead. The pony responsible is Ruby: the ghost of a mare that had inhabited the library since an accident took her life. In order to save Twilight from suffering her fate, she brought her to the Realm of the Dead. With the promise of a way out, Twilight follows Ruby, and together they make several allies on their journey. But not every pony is so willing to let a living soul pass freely through their realm.