Inside Marinette's room, Marinette and Alya have assembled Alix, Rose, Mylène, and Juleka in order to tell them a "huge scoop". Alya tells them that Marinette has a crush on a boy, and Alix and the other girls reveal that they already know her crush is Adrien, Mylène pointing out that it's obvious and she never actually hid this fact very well. Marinette starts to panic, thinking the Adrien knows too but Rose points that boys like Adrien are never aware of that.
Marinette and Alya discuss "Operation Secret Garden"Alya and Marinette introduce a plan called "Operation: Secret Garden", which is to get Marinette and Adrien together while the latter is having a photoshoot in the Trocadéro. Mylène asks why Marinette can't just do the direct approach and ask causing the girls to laugh Marinette can never talk normally in front of her crush. They give the girls their own flower-based codenames, Alix being "Violet", Mylène "Sunflower", Juleka "Rose", and Rose "Tulip", Rose also becoming confused as to why she isn't simply referred to as "Rose" instead of Juleka, but goes along with her name regardless. The plan is then detailed by Alya and Marinette; while Adrien, codenamed "Buttercup", is having his photoshoot by the fountain, Juleka will place a fake parking sign in front of the Gorilla's car, or at least the "Nanny"'s car. and Mylène will alert a police officer so that the Gorilla will have to move. When Adrien is finished with the photoshoot, Alya, codenamed "Tiger Lily", will gesture the group to signal this, and Marinette, codenamed "Lotus", will intercept him. At this point, Rose will signal Théo to drive up with his rickshaw, and Marinette and Adrien will ride up to Andre's ice cream stand. For the final phase of the plan, Alix will skate up on her rollerblades and spread flower petals while Marinette and Adrien eat ice cream together. The girls agree to go along with the plan and prepare to put it into action.
At the Trocadéro, Adrien is still in the photoshoot. Deciding to make the photos more interesting, Vincent rushes off to buy a lollipop, while Adrien waves to a passing child. Vincent comes back with the lollipop, the child, named August, becomes excited at the sight of the candy, but becomes upset as he is taken away from it, and his mother gives him his bottle to compensate. With everyone in their positions, the plan begins to proceed, however, it begins to go awry when Juleka gets the cart carrying the fake sign stuck in a manhole cover, forcing Mylène to help her carry it into position.
Juleka, taking Mylène's place while she holds up the sign, alerts Roger Raincomprix to the Gorilla's "illegal" parking, and the latter is forced to move his car. Meanwhile, August's mother is having trouble getting her son's stroller up the stairs. Adrien notices this but is stuck at the photo shoot. As she continues to struggling, August wants a lollipop but his mom says no and he cries but the problem doesn't go unnoticed by Marinette who wants to help. Until Alya stops her by saying Adrien might see her, once at the top August is still crying until he gets his bottle and calms down. However, at the same time, Rose accidentally signals Théo too early, resulting in him crashing into the Gorilla as he pulls out, getting him yelled at by both Théo and Roger, although Rose gets Théo back into his proper position.
The Gorilla tries to find another parking spot until it's gets taken by a motorcyclist causing him to get irritated and move, at the same time the plan goes as proceed as August's mother struggles to continue up the stairs she drops her phone and Marinette goes to help her although Alya tells her to stay put. Helping them she gives August's Mother her phone, says hello to her son and helps her the rest of the way expressing her thanks. Alya continues to observe Adrien to see he's leaving from the photo shoot and warns Marinette just as they reach the top August drops his bottle causing him to cry until Marinette gets it for him. August's Mothers thanks her and Marinette quickly runs hiding behind a pillar until she notices the Gorilla, causing them to alert Roger again and getting Adrien's bodyguard more irritated. But, his anger doesn't go unnoticed by Hawk Moth and sends his akuma, the Gorilla, August and his mother cross paths and she sees that her son is really fussy today but as Adrien continues to meet him. His joy is turned into shock when he sees the akuma heading straight for him however the Gorilla calms down upon seeing Adrien just enough for it to miss him which leaves Hawk Moth shocked. But the akuma goes towards young August instead which leaves Hawk Moth mortified but goes with the idea and improvises. He tries to get the young boy to understand in exchange for his powers he'll get the Miraculous, but he's more interested in lollipops nevertheless he gets akumatized into Gigantitan. His mother becomes horrified at what happened to her son but since August couldn't see what he was doing, he almost steps on her until Marinette pushes her out of the way. During his quest for a lollipop, August accidentally scares everyone, and he picks up the Gorilla thinking he was a treat. When the young villain discovers he doesn't taste like one, he throws the guard into a tree.
Seeing August's mother showing concern for her son, Marinette assures her that Ladybug and Cat Noir will get him back while taking her to safety. Needing to stop him, Adrien transforms. As the girls reunite Rose asks where is "Lotus" leaving others confused until she clarifies saying where's Marinette they try to find to her but get spotted Gigantitan which causes them to run. Until Cat Noir gets his attention by ringing his bell even though the villain can't reach him he decides to play chase with him bringing the baby villain to an area where he can't do any damage. That doesn't go unnoticed by Marinette who compliments on her partner's cleverness on knowing that her stroll with Adrien would have to wait she transforms into Ladybug. Cat Noir gets caught by the villain and almost put into his mouth until the heroine intervenes and he uses his staff to escape. Understanding that the akuma is in his bracelet she tries to lasso it but gets sent flying to the top of a building where Cat Noir teases her about not being good with kids until she retorts by saying it's not her fault that she never babysat a 10-ton kid.
Seeing the villain's hand the duo backs away using her vision Ladybug sees the akuma is in the bracelet, she tries to get it but he throws her off again. Noticing the tower during her fall she tells Cat Noir it's time for plan B by putting him in a playpen, but he asks where will they find a play pen at the villain's size. She points out the area under the tower where Ladybug explains after she uses her yo-yo to make it, they could sing him a lullaby or tell him stories until he falls asleep while Cat Noir use his Cataclysm to destroy the bracelet. Although, he compliments on the idea he asks how are they suppose to get him there and thought it would be simpler to use her Lucky Charm but all she asks him to do is follow her lead. As they lead him Cat Noir offers to sing to him but she points out that they are suppose to calm the baby down not hurt his ears, however he adds on that he has beautiful voice offers to serenade a song to her causing Ladybug to laugh.
The plan seems to go on perfectly until the baby villain spots the lollipop truck causing him to stop following them however, Cat Noir leaves with an idea in mind. But as the baby tries to get one he accidentally crushes the truck causing him to cry but he hears the beeping of another car with Cat Noir inside; once Gigantitan finds it he starts to play with it leaving Hawk Moth very annoyed. The cat comments that he liked to play with cars when he was little too and the villain starts to go to the tower on his own with Ladybug complimenting Cat Noir on a good job as they continue to follow him. However, Hawk Moth was displeased and commanded him to attack the two heroes but the baby was too busy playing.
Proceeding with the plan Ladybug creates an area with her yo-yo but August is not happy about being in a playpen and pulls on the string. She tells to Cat Noir hurry and he summons his Cataclysm but just as he tried to use it on the bracelet the cat gets sent flying and Gigantitan gets out. Meanwhile, Alix gets impatient about how long Marinette's plan is taking and the hero takes a crash landing into Andre's ice cream stand and comments that his ice cream is the best in Paris but accidentally destroys the cone with his powers although André takes it as a compliment and the cat . At the same time, Ladybug desperately tries to restrain Gigantitan to no avail until Hawk Moth commands the villain to grab her. Seeing what's going on she tells the baby not to put whatever he sees in his mouth which was about to happen to her until Alya and the others intervened causing Gigantitan to release heroine and she expresses her thanks. But, Hawk Moth who was furious told him not to let Ladybug get away but doesn't listen and Cat Noir rejoins her and points out he doesn't have much time left. Finally done with complicated plans she summons her Lucky Charm receiving gift wrap looking around she spots a lamppost and Cat Noir's bell. Alya gets exhausted and the girls ditch the bike and Gigantitan finally gets his lollipop but when puts in his mouth it doesn't taste like one and he starts to cry again. Until Cat Noir calls him over with his bell seeing a real treat he picks it up and finds Ladybug inside she finally manages to break the bracelet and purify the akuma tossing the gift wrap into the air everything returns to normal.
After August is de-akumatized he is caught by Cat Noir and Ladybug compliments that he did a good job taking care of a baby. Soon August and his mother are reunited and just as their transformations are about to wear off they take their leave before saying goodbye while August and his mother express their thanks. However, Hawk Moth claims that his champion wasn't big to cease victory today but he guarantees the next one will be. Marinette reunites with her friends relieved to see them alright and they're all that everything worked out in the end except a date with Adrien. Rose points out that he's coming this way and that they are right to continue with the plan but having enough with complicated plans Marinette tries the direct approach. Getting Adrien's attention he gives her a greeting was surprised to find her here and she explains that she comes here to draw. Marinette tries to ask him if he could hang out with her.
But seeing that his bodyguard is disturbed enough Adrien turns down her offer but offers to give her a ride home. Nearby Alya and the others hope Marinette will say yes but she says she'll take another ride home to her friends surprise and they say goodbye. Once Adrien leaves and Marinette is surrounded by her friends she becomes disappointed that she turned down his offer but the girls praise her for making a good effort. Then, Alix appears and drops rose petals around Marinette's seeing that "Buttercup" has left the garden. Alya doesn't see it as a problem she calls Théo over and they all take a ride before the ending card appear.
Major characters
Marinette Dupain-Cheng/Ladybug
Adrien Agreste/Cat Noir
Hawk Moth
Tikki
Plagg
Akuma
August/Gigantitan
Alya Césaire
Rose Lavillant
Mylène Haprèle
Juleka Couffaine
Alix Kubdel
Minor characters
Adrien's bodyguard
Vincent
Roger Raincomprix
Sabrina Raincomprix (mentioned)
Théo Barbot
André
August's mother
Civilians