A type of disease known as the 'Pony Plague' is ravaging Equestria. It doesn't really physically harm the ponies, but they go into a deep coma that, without a proper cure, is nearly impossible to wake from. This disease doesn't discriminate either, as it will effect not only ponies, but alicorns, minotaurs, dragons, and pretty much any organism that has life other than plants. Twilight is the only pony who has a disease resistance to it. Along the way she learns of her ancestors who had cured Equestria of it long ago. (This story takes place after 'Magical Mystery Cure')