Stolen from Celestia, Twilight is given amnesia and fierce training by Nightmare Moon. In a battle, Nightmare is fatally wounded. Twilight, now known as Eclipse, puts on Nightmare's helmet, and becomes, the Queen of Nightmares, Eclipse Shadow. Does Sunset Shimmer, now the student of Celestia, and risen to alicorn, and her pet phoenix, have the strength to stop Twilight's madness and bring her back? Or will Equestria fall to eternal night?