Miraculous holders from another world appear in Paris. They come from a parallel universe where everything is reversed: the holders of Ladybug and Black Cat Miraculouses, Shadybug and Claw Noir, are the bad guys, and the holder of the Butterfly Miraculous, Hesperia, is a superhero. Ladybug and Cat Noir will have to help Hesperia counter the attacks of their evil doubles and prevent them from seizing the Butterfly's Miraculous. Can our heroes also help Hesperia make Shadybug and Claw Noir better people?

After a guardian of magical jewels turns an awkward girl and a popular boy into superheroes, they can never reveal their identities — even to each other.

On school break, Marinette heads to Shanghai to meet Adrien. But after arriving, Marinette loses all her stuff, including the Miraculous that allows her to turn into Ladybug!