In a strange other-world, the land of Equestria is split in two. Twilight Sparkle, brilliant and antisocial, is the prized pupil of the distant yet gentle Queen Celestia in the east; while Sunset Shimmer, cunning and ambitious, is the protege of the strict yet caring Queen Luna, who rules the west. And indeed, despite the divide, the land has seen peace for centuries.

Yet, all is not well; nonsensical rumors of a third alicorn spreading a message of unity have been making the rounds, and a string of sabotage incidents and mysterious disappearances have been plaguing both nations, with all clues pointing to the opposing side.

Against the backdrop of an Equestria slowly falling apart at the seams, these two must overcome their personal flaws, find friendship in unexpected places, and root out a strange conspiracy if they are to have any hope of stopping their mentors from making a terrible mistake...