Climbing up Oni Mountain, Liko, Roy, Dot, and Friede finally reach the end of the Infernal Pass and arrive at the Crystal Pool at the mountain's summit. They spot a signpost, which informs them of a local legend that says that the Crystal Pool can allow one to see those who have died. However, the person they've come to meet, Briar, is nowhere in sight, so Friede sets out to look for her while telling the children to wait. The trio's first partner Pokémon start playing at the shore of the pond, but their playtime is interrupted when an agitated Milotic suddenly emerges from the water before them and promptly Terastallizes into a Ghost type. Left with no other choice, the children start to battle Milotic, but its movements and counterattacks prove too fast for them. Liko tries to use Floragato's vine to hold it in place, but instead, Milotic ends up pulling Floragato underwater, forcing her to let go. Deciding on using a lure instead, Roy and Dot get an idea from a carnival game that Dot played back during the Countryside Harvest Festival. Floragato ties her vine around Quaxwell, who dances in the shallow water to lure Milotic in, at which point Floragato pulls Quaxwell to safety and Crocalor uses Disarming Voice. Surprisingly, Milotic uses Disarming Voice right back, and soon both it and Crocalor start singing to each other, with Milotic's Terastallized state becoming undone in the process as the two song-loving Pokémon communicate through their singing.
Just as the pacified Milotic dives away, Friede returns with Briar, who explains that Milotic's unprovoked aggression must've been caused by the Crystal Pool's composition. She and the young Rising Volt Tacklers introduce themselves to each other, with Briar having heard of them from Raifort. When the subject of their meeting, Terapagos, emerges from Liko's backpack, Briar goes beside herself with excitement and tries to examine it, only for Terapagos to freak out and run away from her until Floragato manages to calm her down. Briar notes that she has actually seen another awakened Terapagos before, much to Liko's surprise. She also mentions how the crystals in the Crystal Pool resemble those found in Paldea, explaining how wild Pokémon are able to Terastallize in Kitakami as well. She explains that she found this out while researching the Terastal phenomenon, which is heavily connected to Terapagos. Both sides of the conversation are eager to learn more from the other, so they head to Briar's tent nearby. While they set up tables and a campfire, Roy asks Briar who her partner Pokémon is, but she admits that her work has been so busy that she hasn't found herself one yet. Dot finds this relatable, also being very into studying Pokémon, although she does have Quaxwell watching after her.
After settling down, Liko tells Briar everything she knows about Terapagos's history, from her receiving it in the form a pendant from her grandmother to its connection with Lucius, the Six Heroes, and Laqua. While Briar cannot tell them anything about Laqua, she does note that Lucius must've met Terapagos somewhere, just like Heath, the scientist who first named Terapagos and her ancestor. Her dream is to prove Heath's discoveries were true, and she pulls out a copy of his Scarlet Book from her backpack. It is the original tome, where the parts that were made illegible in the printed version are perfectly readable. One part details the expedition that Heath led into Area Zero down in the Great Crater of Paldea. In its depths, he had discovered many shining jewels, a Pokémon that he had named Terapagos, and many other mysterious Pokémon. However, Heath's writings about his discoveries were largely discredited, with hardly anyone believing him. That's why Briar is determined to solve the mysteries surrounding Terapagos and prove that her ancestor was correct. Liko finds the idea relatable, as she too had inherited the quest of solving the mysteries surrounding Terapagos and Lucius from her grandmother, making her and Briar kindred spirits.
Liko shows Briar her grandmother's research notes and Lucius's memoirs, the latter which her grandmother had found in her attic. Examining the memoirs, Briar notices a sketch of Terapagos's Terastal Form, whose name the group hadn't known of before. Briar notes that for Terapagos to change from Normal Form to Terastal Form requires a special impetus or power of some kind. Roy realizes that one of these transformations occurred during an encounter with the Black Rayquaza. While Briar theorizes that Terapagos and the Six Heroes share some kind of unobserved connection, both Liko and Friede recall another incident and ask Briar if she knows anything about the substance called Laquium. Although she doesn't, the fact that there's so many things she's not heard of before only makes her even more excited to uncover everything about Terapagos. After nightfall, Briar leads them back to the Crystal Pool, hoping that Terapagos's memories of Lucius and the location's rumored special properties could help them find some answers. They stand together in front of the glimmering pool while Terapagos call out for Lucius, but despite the legend about the Crystal Pool allowing people to meet those who have died, nothing happens all night. The next morning, the Rising Volt Tacklers leave Briar to continue her research and return to the Brave Olivine. With their leads regarding Terapagos having dried out for now, the team decides to focus on finding the rest of the Six Heroes, although they don't really have any clues regarding their whereabouts either. Murdock notices that Dot is not with them, and Liko tells him that Dot stayed behind in Mossui Town to get some footage for her videos.
In Mossui Town, Dot has just finished recording some footage of the local Pokémon when Quaxwell points out an unusual Growlithe to her. Consulting her Rotom Phone, Dot learns that it is a Hisuian Growlithe. Remembering that Kleavor was also native to Hisui, she quickly follows Growlithe to its Trainer, Perrin, who confirms that her Pokémon indeed comes from her homeland of Sinnoh, once known as Hisui. Dot asks her if she knows anything about Kleavor, but she only agrees to tell her under some specific conditions, the first of which is getting to take a photo of her. While initially shy about the idea, Dot ultimately agrees. The second condition that Perrin declares is for Dot to show her strength in battle, sending out Leafeon to be her opponent. Although Dot immediately realizes that her Quaxwell is at a type disadvantage, she still resolves to fight. After both sides have dodged some of each other's attacks, Leafeon powers itself up with Swords Dance, followed by Leaf Blade. Quaxwell tries to counter the blows with Pound, but is still struck hard. He still gets back up, though, and after dodging some further Leaf Blades, he uses a new move that Dot recognizes as Air Cutter. Dot orders another Air Cutter, which powers through Leafeon's Razor Leaf, so Perrin instead calls for a Quick Attack. Quaxwell succeeds in dodging the fast-speed attack and deals the finishing blow with Low Kick, defeating Leafeon. As promised, Perrin shows Dot a photograph she's taken. Shocked by what she sees, Dot takes Perrin with her to the Brave Olivine's conference room, shocking her fellow Rising Volt Tacklers with the knowledge that Perrin has seen Kleavor, with the young photographer happily introducing herself to the bewildered adventurers.
