Twilight Sparkle and her friends visit the Crystal Empire for her first royal summit following her coronation as a princess of Equestria. Sunset Shimmer, a former student of Princess Celestia, emerges from a mirror portal and steals Twilight's crown. Twilight is tasked with retrieving it from the other world before the portal closes for thirty moons. Despite Celestia's insistence that Twilight must travel alone, Spike follows her into the portal.