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!

Marinette's class is headed to New York, the city of superheroes, for French American Friendship Week, but the American superheroes may find themselves in need of help while there.

By daylight, Marinette Dupain-Cheng and Adrien Agreste are ordinary teenagers. But unbeknownst to their family and friends, the two of them carry a huge secret...using the powers of magical creatures called Kwami, they transform into the superheroes Ladybug and Cat Noir! With a mission to protect the city of Paris from the evil Hawk Moth, the two of them must learn to cope with their new responsibilities, as well as ordinary troubles involving love, school, family, and friends. Most of all, they must learn to put their romantic feelings aside in order to perform their duty, unaware of each other's true identities.