Ash and Goh, having won a lottery prize that allows them to guest star in a Pokémon Circus performance, are joined by Chloe before they enter the circus tent. Inside, they see two trapeze artists practicing, each of them having an Eevee as their partner. They are greeted by the circus's showman, who looks exactly like the excavation leader and the Pewter Museum curator, although he denies being either of those people. Chloe introduces herself and explains she came here because she read that a Flareon and a Jolteon would be performing. The showman reveals that the two trapeze artists, Harmony and Billy, are just about to evolve their Eevee.
Harmony and Billy properly introduce themselves and their respective partner Eevee, Bernice and Toril. They also make their respective interests of the Fire and Electric type more than obvious by claiming their preferred type is superior to the other one. The showman tells them to show Chloe their Eevee evolving, but as the two performers pull out a Fire Stone and a Thunder Stone, they start arguing which one of them gets to go first, with the end result that they accidentally drop the stones, which fall on the incorrect Pokémon, causing Bernice to become a Jolteon and Toril to become a Flareon, much to the shock of their Trainers. Accusing each other of causing this, they try to use spare stones to correct the process, but nothing happens, making them even more dismayed. They complain to the showman that they can't perform like this, so he suggests them swapping their Pokémon for the performance. Despite Ash objecting that they need to consider the Pokémon's feelings, the two performers take each other's Pokémon and leave.
While Ash and Goh practice their own guest performances, Chloe sees that neither Bernice and Toril feels motivated to practice, saddened by being separated from their respective partners. The next day, Bernice unexpectedly joins Harmony's Fire team's rehearsal, while Toril does the same with Billy's Electric team's rehearsal. Since the two Pokémon clearly aren't happy with the partner swap, the showman tells Harmony and Billy to try practicing with their own partners. Ash, Goh, and Chloe arrive to rehearse and are surprised to see the performers practicing their flying trapeze act with their respective partners. While the performers start to see the appeal of their opposing type, they're still not completely satisfied, and the showman fears that the flying trapeze act may end up being cancelled because of this. Harmony and Billy agree and leave to take a break, reassuring their partners that this is not their fault and telling them to stay behind.
Bernice and Toril run out of the tent, followed by Chloe and Eevee, who find the two Eeveelutions practicing together. Ash and Goh join her as well and figure that the two Pokémon must want to perform together. Eevee joins in as well, using Copycat to mimic their moves. Ash is excited and declares that he wants to join in too. While he and Goh start helping the Eeveelutions in their training, Chloe invites Harmony and Billy to watch it too. After some target shooting on frisbees, Bernice and Toril combine Thunder Shock and Ember to create a captivating display of fireworks. Chloe explains to the performers that their Pokémon are practicing hard because they want to be able to perform with their partners. Seeing their partners' determination, Harmony and Billy decide to turn over a new leaf and practice together to put up a great show.
The performance day finally arrives, and Ash and Goh get to show off their guest performances while Professor Cerise, Chrysa, and Ren watch from the audience. Once their performances have been brought to a successful end, Chloe and Eevee appear on the stage as Harmony and Billy begin their flying trapeze act, initially appearing with each other's partners but swapping them for their own ones mid-swing and covering each other's trapeze ropes with their partner's element. Eevee then puts on a fireworks display by launching Embers and Thunder Shocks in succession, soon joined by Harmony and Billy's Pokémon teams. The performance leaves the audience amazed, and once it has concluded, Harmony and Billy thank Chloe for making it a success. As a sign of gratitude, they hand her their spare Evolution stones and give her recommendations of their partner Eeveelutions, this experience having broadened their horizons. Chloe happily accepts these gifts and promises to stay together with Eevee, no matter what she'll eventually evolve into.