After the ship is docked at a port on the coast of Wayfarer Island, the gang arrives at a Pokémon Center, which is at a wooden cabin in the forest. [[Nurse Joy]] tells them that they will find a lot of migrating Pokémon deep in the mountains, and Ash is keen to have a look. Nurse Joy urges them to stay safe and sound.
As they walk up into the mountains, Ash is very excited to see what new Pokémon he can find, which Iris is all too familiar with. Suddenly they run into a patch of Metapod, which Ash scans with his Pokédex. Just as soon as the entry is finished, the Metapod start to evolve. Ash has never seen so many Metapod evolving at the same time. Once the Butterfree start to emerge, Ash scans Butterfree with his Pokédex also. Cilan says that this is the first time he has seen a Butterfree. Cilan has never seen a Butterfree before, while Iris marvels at their beautiful wings. Iris and Ash both notice that the Butterfree are about to begin their migration, and sure enough, they all take off. Ash even notices a second flock of Butterfree flying away from a different location. Everyone is in awe, with Cilan commenting that nature is showing it's delicious recipe for perfection.
Suddenly, a Caterpie emerges from the bushes, looking dazed. Ash scans this with his Dex also. Since Caterpie is destined to evolve into Metapod and then Butterfree, Iris and Cilan deduce that it was not able to evolve with the rest and so it's alone. Seeing Caterpie takes Ash back to the
first he ever caught . Flashbacks show Ash catching his Caterpie and having a good time with it. It then shows his Butterfree migrating with a female Butterfree that it met when Butterfree saved it and they both flew off into the sunset. Ash and Pikachu discuss where Caterpie might be now, coming to the conclusion that it's happy with its new life. Then Ash talks to this Caterpie, trying to get it to evolve, but is frustrated that it's asleep. Suddenly, Ash gets a brainwave and runs off back to the Pokémon Center, much to the surprise of Iris and Cilan.
In a room alone, Ash makes a video call to Professor Oak but is surprised when Rotom answers. After Oak scolds Rotom for playing with the videophone, Rotom electrocutes Oak, leaving Ash shocked. Ash asks whether Oak is alright and tells Ash about Rotom's pranks. Ash asks Oak for one of his Pokémon and says yes.