Like Ash, his classmates, and Professor Kukui, the Meltan have reached Melemele Island and already begun eating their way through several metal items in a boat shed. They soon locate a manhole cover and quickly dissolve it, causing some of them to fall into Hau'oli City's underground pipe network. The remainder looks inside the sewer and later falls in after losing their balance. While exploring the pipes, the first group comes across a curious Alolan Rattata, but they are forced to flee after their attempt to lay still fails. The Meltan soon find a ladder that leads up to another manhole cover, which they quickly absorb. They spot James walking with Meowth and Wobbuffet while carrying a box full of nuts and bolts. Wobbuffet unexpectedly falls over, tripping Meowth and James in the process. The trio gathers all of the metal pieces and places the box back in their Malasada van while they are unknowingly watched by the Meltan. The Meltan soon gain entry into Team Rocket's van, melting their way inside. Meanwhile, the other group comes across a wild Magneton and attempt to melt its metal body, but it is unimpressed and shocks them before leaving angrily.
Over at Bewear's den, Jessie snares Meowth's dessert, a limited edition Paniola Town Pudding a la mode, from the fridge. Meowth and James soon return to headquarters, where the Meltan are shown lying inside the box they recently brought back. Meowth confronts Jessie over his missing dessert, and soon spots it behind her back. Jessie and James demand a share each as tension begins to build over the dessert. Meanwhile, the Meltan leave the box and decide to explore their new surroundings.
Professor Kukui begins his Pokémon School class on building electrical appliances. He announces that everyone will be helping to build Sophocles's designed Pokémon training machine, and Togedemaru demonstrates the running wheel contraption. In the school's basement, a group of Meltan wanders into the Ultra Guardians' base as Clefable busily cleans. Clefable turns around and begins chasing the menaces around the headquarters. The Meltan unintentionally escape using the elevator and find themselves inside the classroom. The little Pokémon quickly eye off Sophocles's tools and jump into the toolbox. Sophocles then asks Ash to fetch him a ring spanner, but Ash fails twice, only for Lana to step and grab the correct tool. Following Sophocles's request, Lillie goes to the toolbox to fetch a bolt, but she returns with a Meltan instead. The students notice that the nut is a little odd, so they begin to prod and poke Meltan's squishy body and eye. Meltan becomes irritated and uses Flash Cannon to free itself.
The ploy works as Lillie drops Meltan and everyone is left confused. Rotom scans its database on the mysterious creature, but its search yields no results. Professor Kukui even admits that he hasn't seen anything like it before. Lillie adds that it may be an undiscovered Pokémon as Sophocles spots more Meltan in his toolbox. Sandy begins to tackle the toolbox in excitement, but the Meltan prepare to retaliate against her. Luckily, Pikachu's Electroweb spares Sandy from being hit by the multiple Flash Cannon attacks. Kukui urges everyone to be careful given how defensive Meltan appears to be. Kiawe attempts to pat the Meltan, but he is electrocuted as a result. Sophocles then relaizes that his tools have vanished, and Mallow suggests that the mysterious Pokémon may have eaten them. Ash goes on to give the Meltan a wrench to test the theory, and the Meltan quickly crowd around the metal object as the class make notes on Meltan's anatomy. Sophocles fetches his electromagnet, and the resulting force causes the Meltan to initially float before bonding together. Kiawe's Marowak decides to welcome the new visitors with a fire dance. It ignites its bone with its head, and the green twirling flame instantly attracts the Meltan. The mysterious Pokémon come too close to Marowak's flame and flee after their bodies becomes too hot.
Meanwhile, Team Rocket have since resolved their dessert crisis, and indulge in a portion each. Jessie and Meowth, however, remain unsatisfied. Jessie's attention then turn to the box of parts, but James is shocked to see that the box is empty. Everyone hears a cry and begin to search the base for its source. The Meltan have melted their way through one of Team Rocket's servers and they soon chew through James's bottle cap collection. Unfortunately, by the time Team Rocket locate their intruders, the Meltan have already melted through the base's central mechanism. Jessie picks up one of the Meltan and James goes on to interrogate it. This only agitates Meltan and it attacks James with Flash Cannon. The surprisingly strong attack instantly frightens the trio, allowing the Meltan to escape.
At the Pokémon School, the class are searching the school's grounds for the Meltan. As the classmates split up to cover more area, one Meltan returns to the classroom and notices Rowlet sleeping on a window ledge. Meltan begins to nap next to Rowlet, but it loses its hex nut after being frightened by Rowlet as it wakes up. A wild Murkrow spots the shiny object, but Rowlet manages to reach the hex nut first and returns it to Meltan. Elsewhere, Team Rocket has managed to surround their menace Meltan. Meowth translates their speech, but he adds that they are speaking nonsense. Jessie eyes off the mysterious Pokémon as potential profit, while James is fixated on avenging his destroyed bottle caps. James sends out Mareanie, but she affectionately smothers her Trainer instead. Jessie calls for Mimikyu's assistance, but its Shadow Ball attack is disappointingly small due to its unwillingness to fight anyone besides Pikachu. Following James's orders, Mareanie attacks the Meltan with Spike Cannon. Meowth tries to net the nuisances, but they retaliate with a combined Flash Cannon. The Meltan attempt a second Flash Cannon, but Bewear, with Stufful on her back, blocks the attacks. Bewear screeches, and the high frequency cry scares the Meltan away. Meowth is furious that their profit has gone, but before Team Rocket can chase after the Meltan they are all scooped up and carried back to the den by Bewear.
Pikachu suddenly spots the Meltan scaling the school's roof towards the bell. The students reach the bell tower in time and Komala strikes the bell which sends the Meltans' hex nut heads into a spin. Lana thinks that the Meltan may be resonating. The generated frequency attracts the attention of the other Meltan group in the forest, and soon the group at the school flees to join the others. Ash and the others are still curious about the mysterious Pokémon, while Rotom is glad to have obtained a lot of new data. With the school day over, Ash grabs his Bag and heads for home.
By the evening, Ash contacts Professor Oak to alert him about the discovery. Rotom sends over its data to Professor Oak's Laboratory. Oak quickly reads through the research notes and is impressed by the amount of data gathered. He then announces that he will continue to study and that he'll update Ash on any new information. One Meltan has secretly sneaked into Ash's bag, while the rest continue to bother Clefable back at the Ultra Guardians' base.