Ladybug and Cat Noir discover that there is a parallel world where the holders of the Miraculous of the Ladybug and the Black Cat are evil while the holder of the Miraculous of the Butterfly is a hero ...

During a school field trip, Ladybug and Cat Noir meet the American superheroes, whom they have to save from an akumatised super-villain. They discover that Miraculous exist in the United States too.