Ash and Pikachu are sleeping in Professor Kukui's house when Ash wakes up and has a look at his Z-Ring and remembers his battle with Tapu Koko where his Electrium Z shattered. Rotom Pokédex goes to wake them up before noticing that Ash is already awake. Ash is hoping to be able to use Z-Moves again and decides he has to get more crystals as Pikachu continues to sleep. During breakfast, Ash explains to Professor Kukui that he wants to get a lot stronger and then have a rematch with Tapu Koko and try the Z-Moves again. Professor Kukui sees that he is really fired up as Ash remembers he can get Z-Crystals by going through the island challenge which Professor Kukui confirms is one way but the most certain way and needs to pass the grand trial of each of the Island Kahuna's. Ash asks how they do it but Rotom Pokédex stops Professor Kukui from answering and explains that a grand trial is a battle with between the challenger and the island Kahuna and if the trainer wins, the Kahuna acknowledges the trainer's worthiness which excites Ash but Professor Kukui says he shouldn't be too over confident as Rotom Pokédex explains that the grand trials come after smaller trials. Seeing Ash's determination to take part, Professor Kukui suggests they first pay Hala a visit as he is the Kahuna of Melemele Island. They leave with Professor Kukui telling Rockruff to guard the house whilst they are gone.
In a field, a large group of Alolan Rattata and Alolan Raticate and eating the fruit when they are confronted by the owner and leave but end up startling three Tauros who are pulling a cart of timber which are sent flying. Along the road, Professor Kukui, Ash and Rotom Pokédex are walking when they spot several villagers cross their path in a hurry and spot the accident that occurred with the Tauros as Officer Jenny informs the villagers that the road has been closed until the timber can be removed as the driver checks on his Tauros who are uninjured. Professor Kukui speaks to Officer Jenny who explains what happened. Ash is surprised as Officer Jenny asks if he is a student at the Pokémon School, which Ash confirms and introduces himself. Officer Jenny tells Ash that she graduated from the school but is distracted when a man and his Hariyama start picking up the timber. Ash notes that the man is strong as Professor Kukui introduces Ash to Hala. Ash goes to help pick up a timber but isn't able to lift it as Hala notices his Z-Ring before lifting the timber that Pikachu was trying to lift as Officer Jenny thanks him for his help. Four Machamp arrive on scene as part of the clean up crew and working together quickly clear the timber as Officer Jenny thanks everyone for their co-operation as Ash tells Hala that he is here for the Island Challenge which Hala already knew as he has been waiting and invites them to his house some time.
The next day, Professor Kukui, Ash and Rotom Pokédex are at Hala's house as Rotom Pokédex takes pictures of Hariyama to update its data, Ash notices a room full of Z-Rings as Hala explains that his Z-Ring is one that he made which surprises Ash as he got it from Tapu Koko. Hala thought this was the case and explains that one day he noticed a Z-Ring was missing and realized it was the work of Tapu Koko and says that this was the first time it had ever happened and tells Ash that Tapu Koko appears to have a strange interest in him. Ash tells Hala that he is keen to get a Z-Crystal as soon as he can for when he plans to battle Tapu Koko again. Hala decides to set Ash a question and tells Ash about the group of wild Rattata and Raticate causing trouble on the island and asks if he was the person tasked with solving the problem, what would he do. Ash responds saying he would use Pikachu and Rowlet and battle them but Hala interrupts him asking if he is curious to know why the island challenge started and explains it wasn't to make trainers stronger but to raise them in a way to protect and love the islands of Alola as well as the people and Pokémon who inhabit them and tasks Ash with looking for answers that won't just lead him to battle as Professor Kukui tells Ash that during his trial, he spent a lot of time thinking about the question as Hala gives Ash plenty of time to think of an answer.
The next day at school, Lillie puts her Pokémon egg on a cushion on a chair as Mallow notes she is now handling the egg with confidence but Lillie says she is always afraid she might drop the egg but Mallow points out she used to be afraid to even tough the egg as Ash struggles to find an answer to Hala's test. Mallow, Lillie and Lana ask Ash what is wrong as Rotom Pokédex calucates he has said hmmn 786 times, much to Lillie's surprise as Kiawe joins them and asks what Hala said offering to help him out. Ash thanks them and mentions the group of Rattata and Raticate and Sophocles is aware of the trouble due to a neigbour and as Ash says Hala asked Ash what he would do with them without using his Pokémon. Lillie suggests if they learn more about Rattata and Raticate, they could come up with an answer as Rotom Pokédex brings up an image of Rattata and Raticate. Ash is surprised that they are different from normal Rattata and Raticate and learns these are their Alola forms as Rotom Pokédex provides Ash with their history, mentioning that groups of Gumshoos and Yungoos were brought in chase them off after their numbers grew which gives them an idea but their delight startles Togedemaru sending her running into Popplio and Bounsweet but Pikachu manages to calm her down.
In a clearing, Team Rocket have escaped from Bewear and are pleased at finally getting away though Jessie can't help but think all the food that Bewear provided was good and agrees that Bewear was a good caretaker but as they walk off, the Rattata and Raticate cross their path and send them flying but as they are delighted to be blasting off, they are caught mid-air by Bewear who carries them back to its den. Meanwhile Ash has suggested his idea to Hala who calls it a wise and thoughtful idea and says it is his idea too and tells Ash honestly that that his question was merely to test Ash to see if he has what it needs to go through the trial as Ash confesses that he had help from his classmates, fearing it might be wrong of him but Hala says that when searching for lives answers, they should look for answers with friends and they leave as a Psyduck falls out of the sky. Ash and Hala arrive at Verdant Cavern, Hala explains that there are several Gumshoos and Yungoos living in the cave who are very strong but there is one Gumshoos who is very strong, it is called a Totem Pokémon and explains there are several Pokémon called Totem Pokémon who follow the lead of the Island Guardians as they assist trainers who take part in the Island Challenge and informs Ash his challenge is to take on the Totem Pokémon in a battle and be victorious and with the aid of the Totem Pokémon to chase away the Rattata and Raticate. As they go inside, Ash asks why Gumshoos and Yungoos would team up with him but Hala isn't concerned and tells Ash if he can earn the Totem Pokémon's respect during the battle challenge, it will assist Ash in his time of need.
Ash is surprised by how huge it is inside as Hala calls out to the Totem Pokémon informing it that there is a trial goer as Ash calls out to challenge it as a Yungoos appears along with a Gumshoos. Ash asks if they are a Totem Pokémon but Hala informs Ash that they are the Totem Pokémon's allies and he has to battle them first. Ash asks Rotom Pokédex for data on Yungoos and Gumshoos which he receives and learns that they are both Normal-types. Ash sends Pikachu to battle and brings out a sleeping Rowlet to assist but Ash soon wakes Rowlet up and the battle begins with Ash ordering Pikachu to use Thunderbolt and Rowlet to use Tackle but Gumshoos blinds them with Sand Attack, preventing their attacks from hitting before launching another attack.