Marinette Cheng-Dupain is the daughter of Sabine Cheng and the mayor of Paris Tom Dupain's stepdaughter. For her sixteenth birthday, her mother gave her a family heirloom. It's a puzzle box that no one in the family has been able to solve. However, she manages to find a way to open a secret compartment within the puzzle box, giving her a set of ladybug-themed earrings. Now she finds herself becoming a ladybug-themed heroine who has to stop those wielding similar pieces of magic jewelry known as Miraculous.