A few weeks have passed since King Sombra and the Tantabus were defeated. The portal that linked the two worlds was destroyed but still there are occurrences of creatures crossing dimensions, keeping the girls from Crystal Prep and Canterlot High busy. Meanwhile, after the incidents with the Sirens and the mysterious geodes, Sunset Shimmer starts to wonder one thing: how did this world become connected to Equestria in the first place and why were so many exiled here? As a new threat emerges, the girls realize the answers they seek lie in Canterlot High itself.