In Chloé's room, Chloé is going through her closet and complaining that she has nothing to wear. Hearing a noise, she goes to investigate and is attacked by her floating skin care bottles. The invisible force steals the shoes away from her and throws across the balcony into the Agreste mansion courtyard. Chloé futilely yells for them to come back.
At school, Chloé is and looks exhausted, almost falling asleep at her desk. Marinette and Alya notice this and wonder if it's because Chloé's friend, Sabrina, is missing, although Ms. Mendeleiev shushes them. Chloé's hair is then pulled, resulting in her shouting in pain and being reprimanded by Ms. Mendeleiev. Chloé tries to explain that something invisible is harassing her, but she isn't believed, with the class laughing at her. Ms. Mendeleiev shushes the class.
The invisible presence grabs at Chloé's purse, trying to take it off her. Even with this occurring, Ms. Mendeleiev still does not believe Chloé. Chloé is thrown back from the invisible presence letting go of her purse only to hit her in the face repeatedly with said purse, resulting in Ms. Mendeleiev yelling at Chloé to sit in her seat. Chloé throws the purse away, cowering in the corner of the room. Both Marinette and Adrien watch, focused.
Juleka's pen is snatched from her fingers and is thrown at Chloé. Several more pens are thrown at Chloé, making her run down the steps. Ms. Mendeleiev yells at Chloé to stop running and return to her seat. Before she can do so, the invisible presence takes Chloé's sunglasses from her head, fighting with Chloé for them. The presence leads Chloé over to Miss Bustier's desk and abandons the sunglasses, instead tugging at Chloé's hair. The entire time, the class laughs at her. Chloé flees from the room, waving her hands in front of her to ward off the invisible presence. The invisible presence follows Chloé, moving Adrien's tablet in the process. The door closes behind it resoundingly.
Both Marinette and Adrien immediately ask if they can go to the bathroom. In the girls' bathroom, crude drawings of Chloé and multiple instances of Chloé's name being scratched out are present on the walls and stall doors. A set of pictures is then sent to everyone in the school depicting what has been happening to Chloé. Marinette, Tikki, and Adrien realize that something must be done to help her and the two of them transform into Ladybug and Cat Noir.
Outside Le Grand Paris, Mayor André Bourgeois is giving a press conference, saying that attacking his daughter is like attacking all of Paris. Ladybug and Cat Noir show up behind the mayor, saying they will help him. Back in Chloé's room, André announces that Ladybug and Cat Noir are there to help, prompting Chloé to rush out from behind one of her couches and tackle Ladybug in a hug, much to Ladybug's annoyance. Chloé then does not leave Ladybug alone the entire time she is in her room, taking several selfies with and pictures of Ladybug. André explains the situation to Ladybug while Cat Noir searches Chloé's room.
Ladybug turns on Chloé's television, turning the four sections of the screen to various areas in the hotel where the invisible presence could be hidden. These include three different angles of the hotel's foyer and Chloé's balcony. Ladybug asks Chloé if she's had any problems with anyone recently, which Chloé denies, saying everyone loves her. Ladybug picks up a picture off the ground and asks about the girl who is in it with Chloé, Sabrina. Chloé says it's impossible for Sabrina to hate Chloé; Sabrina "worships [her]. [She's] her idol." Ladybug sighs and tells the mayor to keep Chloé inside as the invisible presence can't go through walls and won't be able to attack Chloé. Ladybug and Cat Noir then leave, heading down to the hotel's entrance.
Downstairs, they ask Butler Jean what he knows of Chloé and Sabrina, saying that it will remain between them. Jean tells Ladybug of a game that Chloé and Sabrina liked to play called "Ladybug and Cat Noir," where Chloé would dress up as Ladybug and Sabrina would dress up as Cat Noir. Two days previously, they were playing this game with the butler as the villain "Big Mustachio." Ladybug interrupts Jean's retelling to ask who Big Mustachio is, only to find out that it was Chloé's idea.
Continuing with his story, Big Mustachio hid in the lounge area of the hotel where Jagged Stone was being interviewed by Nadja Chamack. "Ladybug" and "Cat Noir" burst in the room, prompting the man at the bar and the people on the couches to turn their attention to them. Immediately, Chloé recognized Jagged Stone and approached him, sitting between him and Nadja.
Jagged Stone believed that Chloé was the actual Ladybug, prompting Chloé to lie between her teeth that she was there to meet Jagged. Noticing her hair was different, he asked what she did with it, her reply is that she needed a new hair style. The entire time, she was being filmed. She then took over Jagged Stone's interview, forcing Nadja to direct questions to her
Sabrina, however, found Big Mustachio and called Chloé by name. Jagged Stone and Nadja became angry at being deceived. Chloé protested, saying she was Ladybug. Her proof was her taking her yo-yo and bouncing it up and down, hitting Fang's head each time. Annoyed, Fang bit the yo-yo's string and ate it, the remaining string hitting Chloé in the face. Nadja and Jagged Stone laugh as Chloé ran off crying. Staring at Sabrina, Chloé ripped off her mask.
Sabrina and Jean followed Chloé to her room, Sabrina trying to apologize. Sabrina didn't know that Chloé was pretending to be the actual Ladybug apart from their game. Angry, Chloé said that Sabrina never knew anything and that even Fang was smarter than her. Chloé threw the yo-yo remains at Sabrina and told her she never wanted to see her again.
Chloé is watching Jean, Ladybug, and Cat Noir from the television in her room.
Sabrina came back the next day. Chloé ignored her the entire time, saying that she didn't know any Sabrina. Sabrina tried to get Chloé, her best friend, to turn around, even holding out the rose pin that Chloé gave her as a symbol of their friendship. Jean approached Chloé, asking her to speak to Sabrina since she's right there. Instead, Chloé said that she couldn't see anyone, that she must be invisible, because, in her eyes, Sabrina didn't exist. Crying, Sabrina closed the door and left.
Ladybug and Cat Noir come to the conclusion that the invisible presence is Sabrina and that she was akumatized. In her room, Chloé has determined that it's impossible for Sabrina to be akumatized, let alone attack her because Sabrina's too afraid of Chloé.
Downstairs, Ladybug thanks Jean for his help. He leaves. Spinning, Cat Noir grabs a flower and offers it to Ladybug who in turn places it in the vase next to her with several other roses. It won't be easy to find someone who can't be seen, so the two decide to wait for Sabrina to find them. Ladybug says that they have the advantage since Sabrina doesn't know that they're there, but Sabrina is behind them. As Ladybug and Cat Noir wander off, Sabrina picks up the flower and twirls it in her fingers. Her face lights up purple as Hawk Moth speaks to her, calling her "Vanisher." Hawk Moth commands her to bring him the Miraculouses, to which she responds by saying they won't see her coming.
Vanisher drops the flower, making enough noise for Cat Noir to turn back. Since he stopped walking, Ladybug turns to see what caught his attention. As Cat Noir begins to explain, the hair around Ladybug's left ear moves. Cat Noir jumps forward, bringing out his staff. He and Ladybug stand back to back, his staff and her yo-yo making circles for defense.
In her room, Chloé decides that if Sabrina is Vanisher, then she will be the one to defeat her. She opens her closet and presses a button on her remote, revealing a Ladybug costume complete with a wig, mask, earrings, and yo-yo.
Back in the lobby, Vanisher proceeds to throw chairs and vases at Ladybug and Cat Noir, the two heroes either dodging or breaking said objects. Ladybug summons her Lucky Charm, this time being a container of red glitter. When it lands in her hands, Chloé appears on the hotel's stairs, dressed as Ladybug and taunting Vanisher. Ladybug tells Chloé to move, prompting her to descend the stairs and tell Vanisher that if she stops, then she might become her best friend again.
Angry, Vanisher throws books at Chloé. She dodges it only because Ladybug tackled her to the ground and because Cat Noir used his staff to block any remaining books. Chloé continues to taunt Vanisher even when Ladybug moves Chloé out of the way. Vanisher runs up to Ladybug and grabs her while Cat Noir searches for Vanisher in the background. Trapped in Vanisher's arms, Ladybug opens the glitter, drops the container on her knee, and pops it into the air, the container turning so that it covers Vanisher in pink and red sparkles. Ladybug rolls, freeing herself.
Vanisher threatens that even though Ladybug can see her that doesn't mean she can defeat her. Cat Noir extends his staff in front of Vanisher, drawing her attention to him as he slides down it and away from Ladybug who is removing Chloé from the scene. Ladybug hides Chloé again and tells her not to move, returning to Cat Noir. Ladybug decides the akuma is in Sabrina's bag, to which Chloé protests. She comes out of hiding and swings her yo-yo, losing control as it breaks and knocks Vanisher in the head and drawing her attention.
Ladybug asks Cat Noir to deal with Vanisher while she deals with Chloé. Cat Noir traps Vanisher's arms while Ladybug lassos Chloé and spins her into an elevator destined to the penthouse. Chloé tells Ladybug that the akuma has to be in the brooch that Vanisher is wearing since it was a gift from Chloé. Annoyed, Ladybug tells Chloé that her being in the battlefield puts everyone in danger. Ladybug presses a button to a higher floor as Chloé protests.
Back in the battle, Vanisher throws pots at Cat Noir, trapping his head in one. While he struggles to get it off, Ladybug grabs Vanisher's bag and rips it open, spilling its contents on the floor. No akuma comes out. Angry and using Ladybug's confusion, Vanisher rushes at her. Ladybug blocks her arms. At the same time, she notices a rose glittering excessively on Vanisher's chest: the brooch. Ladybug pins Vanisher to the elevator doors, forcing the brooch to fall and allowing Ladybug to step on it. The akuma flutters out in the direction of Chloé's camera (she's watching from her room and is annoyed with Ladybug for not listening to her). Ladybug captures the akuma then uses Miraculous Ladybug, returning everything to normal.
In his lair, Hawk Moth growls at his window.
Sabrina returns to normal, cradling the brooch when she realizes she almost lost it. Ladybug smiles and holds out her fist for Cat Noir to bump, but instead, he asks why she didn't listen to Chloé, as she was only trying to help. Ladybug responds that it was Chloé who put them in danger and then lied; Ladybug doesn't listen to liars.
Watching in her room, Chloé is outraged by what Ladybug said. She was Ladybug's biggest fan, but since Ladybug called her a liar, she felt as if Ladybug didn't deserve her devotion. Throwing the television remote to the ground, the channel changes to TVi with Nadja Chamack. Ladybug, Cat Noir, and Sabrina leave the building. Before they can clear the entryway, they are attacked with a barrage of questions by reporters.
Chloé decides she doesn't want to hear any more of Ladybug. This prompts Hawk Moth to reopen his window and send out another akuma.
Chloé rips off her Ladybug mask and stomps on it. She then falls to her knees, crying. The akuma lands on Chloé's left earring, connecting her to Hawk Moth. He offers her an alliance to defeat Ladybug, which Chloé agrees to, transforming into Antibug.
During her interview, Ladybug realizes that she is going to detransform attempts to leave the scene only to be interrupted by Antibug. Where she tells Ladybug that if it weren't for her, she wouldn't have defeated Vanisher, and now she was going to defeat Ladybug. Antibug's taunt makes the heroes recognize her as Chloé. Ladybug tells Cat Noir she is about to detransform and he tells her he can handle Antibug. Where she teases Ladybug, saying that she's nothing without Cat Noir. Ladybug promises Antibug that they'll see each other again soon before dashing off and detransforms. Upon detransforming, Marinette quickly realizes that she has no food for Tikki. Marinette laments how the whole situation is her fault, but Tikki tells her otherwise. They both sneak off to The Palace to find Tikki something to eat. After grabbing some cookies for Tikki, Marinette rushes to find Cat Noir only to find him hanging from a pole hoisted by Antibug. She taunts Cat Noir only for him to retort. Hawk Moth suggests using Cat Noir as bait. Antibug tries to convince Cat Noir to team up with her, but he refuses.
In the distance, Marinette wants to help but Tikki doesn't have enough energy. Tikki tells her that she can save Cat Noir as herself but Marinette is unconvinced claiming on Ladybug could. Tikki then tells her she is Ladybug and that Ladybug is within her. Marinette agrees that she needs to save Cat Noir and comes up with a plan. She uses her cellphone as bait and plays the interview from earlier to fool Antibug into thinking Ladybug is nearby. While Antibug is distracted Marinette saves Cat Noir by taking the pole and using it to pull him up. Once Antibug discovers she's been played, Cat Noir shows up and begins to attack Antibug. Tikki has also gained enough energy, allowing Marinette to transform into Ladybug once more. Ladybug finds Cat Noir as Antibug continues her attacks. Ladybug suggests that the akuma is in her yo-yo, while Cat Noir says it's her earrings, as she had them before her transformation.
Ladybug and Antibug both attack each other simultaneously. Ladybug summons her Lucky Charm while Antibug summons her Anti Charm. When Antibug ends up with a large weapon and Ladybug a bag of marbles, Antibug taunts her and proceeds to attack. Ladybug, searching around, realizes the purpose of the marbles when she looks at Cat Noir. She throws them at him, and he whacks them, releasing the marbles onto the ground and tripping Antibug. Fallen down and her sword taken by Cat Noir with his staff, Antibug complains that Ladybug is weak to rely on Cat Noir. Ladybug replies firmly that she and Cat Noir are a team. Cat Noir uses Cataclysm to trap Antibug into the glass floor beneath her, and Ladybug grabs her earrings. Destroying them, she de-evilizes the akuma and utilizes the Miraculous Ladybug to fix everything. Ladybug apologizes to Chloé about not taking her advice, which Chloé accepts and once more becomes Ladybug's biggest fan. Before departing, Ladybug suggests to Chloé that she make amends with Sabrina.
Back in class, Marinette is sitting with Alya as she watches Chloé sit down. Sabrina enters the room and stands still next to the seat until Chloé tells her to sit down. Sabrina gladly accepts, and while looking away from her, Chloé makes a small smile. Afterward, Chloé gives Sabrina a new brooch, much to Sabrina's joy and Chloé's secret contentment. Marinette comments that Chloé and Sabrina will always be best friends in their weird way, just like she and Alya. The end card is of Marinette and Alya being happy while Adrien, sitting in front of them, is amused.
Characters
Major characters
Marinette Dupain-Cheng/Ladybug
Adrien Agreste/Cat Noir
Hawk Moth
Tikki
Plagg (non-speaking)
Akuma
Sabrina Raincomprix/Vanisher
Chloé Bourgeois/Antibug
Minor characters
Max Kanté (background)
Lê Chiến Kim (background)
Nino Lahiffe (background)
Alya Césaire
Ivan Bruel (background)
Ms. Mendeleiev
Mylène Haprèle
Alix Kubdel (background)
Rose Lavillant (background)
Nathaniel Kurtzberg (background)
Juleka Couffaine (background)
André Bourgeois
Nadja Chamack
Butler Jean
Wang Fu (background)
Jagged Stone
Fang
Roger Raincomprix (background)
Caline Bustier (background)
Pigeons
Civilians