The city of Camelot had been a peaceful place to live until one day a supervillain calling herself Mariposa appeared and began to turn the citizens into monsters with her akumas. Thankfully two superheroes rose up to fight her, the heroine Ladybug and her partner Chat Noir.

Outside of costume, Ladybug is Gwen Smith, a normal high school girl who one day came into her room above her father's workshop to discover someone had left her a pair of earrings that turned out to be the Ladybug Miraculous. She's a shy girl at first, but she slowly grows more confident during her time as Ladybug. She has many friends, including her best friends Morgan Pendragon and Merlin Emery, as well as a crush on a boy a year above her, Lance Dulac. However, as time passes, she finds herself drawn to her partner in justice as well.

On the other side, Chat Noir is a high school boy named Arthur Pendragon who was left the Cat Miraculous. The spoiled son of the city's mayor, he appears brash, arrogant, and selfish at first glance. Looking deeper though, he has a pure heart and slowly learns how to show it during his time as a hero. He attends the same school as Gwen, though he is a year above her and his adopted sister Morgan. Though he'd never admit it to anyone, he has a crush on the younger girl and as a result, eventually ends up spurning Ladybug's affections when the time comes. He's friends with quite a few other boys that go to his school, including a tagalong Merlin. Two years younger, yet in the same grade as Arthur, the boy had transferred into Arthur's school around the same time that Mariposa made her appearance.

Under the instruction of the Guardian of the Miraculouses - an elderly man named Gaius - and using the powers of creation and destruction gifted to them by the Ladybug and Cat Miraculouses respectively, the two work together to free the people from Mariposa's control and try to track her down to retrieve the missing Butterfly Miraculous.

There's more going on than meets the eye though, for the Butterfly Miraculous was not the only one to go missing and there's a past hidden that's waiting to be discovered.

One piece of the puzzle comes to light when Mariposa realizes someone is helping Ladybug and Chat Noir from the shadows, so hidden that even they do not realize the assistance they're receiving. She recognizes the signs though and becomes infuriated when she realizes her old partner is working against her. She becomes so distracted in drawing him out that her assistant turns against her, stealing her miraculous and using her anger to turn her into the monstrous Chimera.

After she's freed from the akuma, she begins to plot how to recover her miraculous. She doesn't get far though, as that night a visitor arrives at her home.

She smirks at the sight of a dragon-winged cloak, but freezes when it is not her partner who steps out of the shadows. The new Dragon Miraculous holder refers to himself as Dragoon and is far younger than Bal Ambrose, or Kilgharrah as his hero persona had been known.

She expects him to ask after the Butterfly Miraculous, but he reveals that he already knows she lost it. Fear floods though her as she realizes why he actually came and she tries to flee, but he catches her before she can even leave the room.

His power washes over her with a call of "Dragon's Breath."

Nim Way is placed in her bed, her memory of the Miraculouses, their abilities, and their holders wiped from her mind.

Dragoon then returns to his own home, detransforming and raising his hands to catch the little white dragon kwami that falls from his necklace. A necklace which is hidden moments later by a bright red neckerchief.