As Team Rocket's evil project of "Operation: Tempest" continues to thrive, Unova is now in its greatest peril ever as they lift the Undersea Temple to the surface of Undella Bay along with the captured Meloetta, and the recording of Meloetta's song in which they've successfully obtain the Reveal Glass. Now, they're going to summon the three Legendary Pokemons of Tornadus, Thundurus, and Landorus by a beam of light of the Reveal Glass which causes Meloetta to suffer. Now that they're all in one place, the Therian Formes of Tornadus, Thundurus and Landorus reveal themselves through the Reveal Glass. But as Giovanni attempts to take control of the three Therian Pokémon, they take over him and drive him to the brink of insanity and ordering them to use the power of "Wind", "Thunder", and "Land" all over the Unova Region. Can Ash and co. save everyone in Unova and stop Team Rocket once and for all?