Marinette's parents are celebrating their twentieth anniversary, leaving Marinette to take care one of her father's special cake requests. However, she gets a call from Alya, who reminds her to bring a banner she made for a race between two of her classmates, Alix and Lê Chiến Kim, and she rushes off to Trocadéro. Alix has received a family heirloom pocket watch for her fifteenth birthday, and passes it to Alya to safeguard it for her while racing. However, during the race, the watch passes hands multiple times, before it is dropped by Chloé onto the ground and skated over by Alix, destroying the watch. Angry at her friends, Alix is attracted to Hawk Moth's akuma and turns into "Timebreaker", a speedy villain who freezes people and fades from existence with a touch to get energy to travel back through time. To make matters worse, Marinette forgot to return to her baker shop to deliver the cake so by chance, Ladybug goes back in time with "Timebreaker" to resolve all the problems because of a broken watch. Not to mention that both Hawk Moth and later Cat Noir has to deal with two "Timebreakers" and two "Ladybugs"!