When Tikki tries to stop Plagg from eating a piece of cheese in the classroom, Ms. Mendeleiev, Collège Françoise-Dupont's physics teacher, catches them, but they escape. Ms. Mendeleiev tries to prove the existence of the magical creatures on a TV show, but the viewers are not convinced by her theory. Marinette and Adrien become convinced that their partner must be one of their fellow students, and Adrien even specifically suspects Marinette; conversation reveals that they must give up their Miraculouses if their identities are compromised, even to each other. Angry that no one believes her theories, Ms. Mendeleiev gets akumatized into "Kwamibuster", a Ghostbusters-themed villain with a vacuum to capture kwamis. Both superheroes lose their kwamis to Kwamibuster, so Adrien hides in a costume, and Marinette flees to Master Fu. She borrows many other Miraculouses despite the physical risk, and has Mullo of the Mouse Miraculous transform her into "Multimouse", giving her the power to divide herself into miniature clones. Some of her clones also use "unify" to undergo alternate transformations and employ the various kwamis to best Kwamibuster, freeing all the captured kwamis. Multimouse then uses the Fox Miraculous to make it appear that Marinette and Ladybug are two different people to erase any idea from Cat Noir of them being the same person. Cat Noir apologizes to Ladybug for his kwami being at "that elementary school" (to convince her that he is not a student there) and discourages Ms. Mendeleiev from making any more attempts to prove the kwamis are real. Marinette returns all of the extra Miraculouses to Master Fu. He remarks how exceptionally strong Marinette is to have used so many at once.

Marinette and Kagami find themselves teamed up in a cross-Paris scavenger hunt to win time with Adrien. Kagami's mother is against her participation and becomes akumatized into the giant centaur mecha Ikari Gozen, who can swallow people up and imprison them inside her armor.

Ladybug and Cat Noir challenge the Bourgeois couple. Now Heart Hunter, a two-headed Cerberus that devours all the love in Paris.

Hawk Moth akumatizes Chloé into Miracle Queen to make her take control of all Miraculous holders. Will Ladybug and Cat Noir be able to escape this fatal plan?

When Tikki tries to stop Plagg from eating a piece of cheese in the classroom, Ms. Mendeleiev, Collège Françoise-Dupont's physics teacher, catches them, but they escape. Ms. Mendeleiev tries to prove the existence of the magical creatures on a TV show, but the viewers are not convinced by her theory. Marinette and Adrien become convinced that their partner must be one of their fellow students, and Adrien even specifically suspects Marinette; conversation reveals that they must give up their Miraculouses if their identities are compromised, even to each other. Angry that no one believes her theories, Ms. Mendeleiev gets akumatized into "Kwamibuster", a Ghostbusters-themed villain with a vacuum to capture kwamis. Both superheroes lose their kwamis to Kwamibuster, so Adrien hides in a costume, and Marinette flees to Master Fu. She borrows many other Miraculouses despite the physical risk, and has Mullo of the Mouse Miraculous transform her into "Multimouse", giving her the power to divide herself into miniature clones. Some of her clones also use "unify" to undergo alternate transformations and employ the various kwamis to best Kwamibuster, freeing all the captured kwamis. Multimouse then uses the Fox Miraculous to make it appear that Marinette and Ladybug are two different people to erase any idea from Cat Noir of them being the same person. Cat Noir apologizes to Ladybug for his kwami being at "that elementary school" (to convince her that he is not a student there) and discourages Ms. Mendeleiev from making any more attempts to prove the kwamis are real. Marinette returns all of the extra Miraculouses to Master Fu. He remarks how exceptionally strong Marinette is to have used so many at once.

Ladybug and Cat Noir challenge the Bourgeois couple. Now Heart Hunter, a two-headed Cerberus that devours all the love in Paris.