There's always some air of mystery and uncertainty when the magical map in Twilight's castle activates, but after a long period of dormancy it summons Twilight with a most perplexing image: two cutie marks as usual, but both are hers, and they alternately orbit over Ponyville and float over the edge of the map entirely. To find the answer to what the Map is asking of her, Twilight turns not just to her student, Starlight Glimmer but must also travel to the parallel dimension of Canterlot High to consult with her alternate self and Sunset Shimmer.
The combined brainpower of three magic savants and one scientist should be enough to puzzle out the Map's intentions, but none of them can guess where the path will lead them.