Parisian teen Marinette transforms herself into superhero Ladybug to find her lonely secret crush Adrien when he runs away from home at Christmas.

Marinette, Adrien, and their friends want to actively fight plastic pollution in Paris. The adventure leads Marinette to realize that the group should try to fix the problem at its root, by trying to meet with the largest plastic manufacturer in person and convince him to change his habits — but supervillain Monarch has other plans.