Twilight finds a strange spell in a book in her library, She reads it, and the next thing she knows she's in a world where everything's turned upside down... literally! She seeks the help of her friends only to find that they're corrupted!

Meanwhile, Twilight's alternate and corrupted version, Twilight Sorrow, finds herself in the bright and wondrous real world - or alternate world in her case - where all of her so-called "friends" are... happy?