Our heroes visit Aether Paradise, part of the Aether Foundation run by Lillie’s mother, Lusamine. An impressive variety of Pokémon live in the conservation area, including a group of Ditto who need their shots! Professor Burnet recruits Ash and friends to help with the vaccinations while Lusamine is busy on the phone, but one of the Ditto escapes and leads our heroes on a merry chase as it keeps transforming. They eventually catch it when it disguises itself as Snowy—and Lillie realizes she can’t touch it!
Meanwhile, the Team Rocket trio has scored jobs at Aether Paradise, and they’re hot on Nebby’s trail when they stumble into Faba’s mysterious laboratory…
Lillie writes in her diary about the events of the previous episode, where Nebby teleported everyone. The next day, Ash and his classmates are on a boat heading to Aether Paradise. They arrive and are greeted by Wicke and Faba, alongside a disguised Team Rocket. Faba annoys Lillie before inquiring about Nebby and goes to grab it, but fails when Nebby teleports away. Faba and Wicke take them to Lusamine as Team Rocket recall being hired by Faba after he took an interest in Meowth. They plan on stealing all of the Pokémon including Pikachu and Nebby. They arrive at Lusamine's home where she greets them only to be interrupted by a phone call.
After the phone call, Ash and the rest of the gang are served food by Team Rocket, much to the trio's disappointment. Lusamine finishes her work and chats with Lillie. Lillie isn't happy with her mother as another phone call interrupts them. Having had enough, Lillie decides to give everyone a tour herself. Faba follows them in pursuit of Nebby. Wicke and Team Rocket accompany them. They arrive in the conservation area and the gang comment on the size of the area and the variety of Pokémon. Looking around, they watch as Professor Burnet emerges from the water with her Munchlax. She was checking the water for the conservation area Pokémon.
The tour continues as Wicke and Professor Burnet explain the history of the Aether Foundation. Nebby leaves Ash's backpack and Team Rocket make plans to capture Nebby. They head to a small building where a group of Ditto reside. They are being kept isolated to avoid them transforming into other Pokémon that are in the conservation area. They go inside where the gang helps give the Ditto their vaccinations. Professor Burnet give the Ditto their vaccinations but the final Ditto jumps out of Lillie's hands and escapes outside. Nearby, Team Rocket, believing Nebby to be a pre-evolved form of Koffing, are pulling around a huge bag of trash in an attempt to lure Nebby to them. Faba comes to tell them about the escaped Ditto, only to be disgusted by the horrible smell of Team Rocket's trash bag. Lillie apologizes for not stopping Ditto from getting away as they suspect Ditto may have transformed into another Pokémon.
At that moment, they notice a second Rotom Pokédex and realize that Ditto has transformed. Ditto disappears among the other Pokémon, leading the others to chase it, using Ditto's specific eyes to help identify it. They soon confront Ditto disguised as a Psyduck before it turns into Snowy, but Ash manages to catch it before it can transform again. Ditto finally receives its vaccination as Wicke and Professor Burnet discuss the aims of the Aether Foundation. Lusamine arrives and starts to embarrass Lillie about managing to find and capture the Ditto before her phone rings and she leaves. Faba heads off, worried that Lillie might start recalling memories and which would cause him problems. Team Rocket continue their search for Nebby down in the laboratory area and spot an open door and head in. Inside the laboratory, they find pictures of Type: Null and documents about the Ultra Beasts. Meanwhile, Nebby appears in front of Team Rocket before quickly disappearing after they attempt to catch it. Faba confronts them, unhappy at their presence in the restricted area. They all decide to agree that they saw nothing.