After departing from Khana's Poké Ball Factory, Liko and Roy do some training with Friede and Captain Pikachu. However, during the battle, Fuecoco slips on a strange purple liquid on the ground, crashing into the barrier surrounding the Wing Deck. As the group notices the purple liquid on the battlefield, Cap sees a Pokémon draped in shadow by the door of the Observation Deck.
As night falls, Liko tells Diana about the purple liquid that Roy is trying to investigate. Liko puts the books she is carrying on the table next to Diana, and then gets the feeling that she is in the way. But Diana is fine with Liko's company, or the comforting sound of her voice. Liko notices a chipped teacup, but Diana tells her to leave it be, because there's something she wants to test. Liko suddenly hears a strange clinking sound. Diana tells her granddaughter to check it out if she's feeling curious. She gives Liko extra incentive knowing that investigating mysteries like a detective is something she likes doing. Looking at her Pokémon, Liko is quick to gather up the confidence to admit it herself as she goes off to have fun with solving the mystery.
Roy and Fuecoco have trouble finding that purple liquid from before, until the mysterious Pokémon Cap caught a glimpse of leaves some from them to find. When they leave the area, the Pokémon joyfully reveals itself as a Polteageist. Meanwhile, Liko can't seem to find out where that clinking sound came from. Sure enough, the clinking sound catches Liko's attention again when Polteageist appears outside and runs into Pawmi, dropping its tea cap on the floor. She follows the sound to see what she finds, but to no avail. Liko hears Rockruff barking followed by the same clinking sound and goes to check it out, but gets baffled even more upon see nothing there.
Dot goes to the refrigerator to get some of Shuckle's juice, but sees that there's hardly any left. Upon seeing Shuckle arrive, Dot grabs him and tries to slurp the juice straight out of its shell with a straw. Shuckle doesn't like this and pours Dot some cups of juice from its shell instead. Muk watches Dot, who says that Shuckle's juice is the best, and Polteageist, who is stuck to Muk's back, is shocked to hear this. As Dot leaves, Muk heads into the kitchen and greets Shuckle. When Polteageist gets unstuck from Muk, Cap catches the Black Tea Pokémon. Polteageist angrily points at Shuckle, wanting to challenge it to a fight. Cap is alright with letting Polteageist settle things its way. Shuckle approaches very slowly, so Cap has Snorunt push it over to them.
Liko is in her room, having to decided to get some sleep and investigate the clinking sound tomorrow. However, she doesn't have long to rest, as the clinking sound is heard yet again. Roy is about to give up his search too, but spots the purple liquid left by Polteageist again. Liko finds Quaxly, who is looking awfully suspicious. Roy and Fuecoco arrive as well, to Quaxly's dismay. Liko and Roy hear crashing from the Hold and find the Brave Olivine's Pokémon gathered together, cheering on Polteageist and Shuckle as they battle. Roy scans Polteageist with his Pokédex before Liko notices Terapagos with the Pokémon as well. After Polteageist and Shuckle taunt each other, Shuckle scores a hit. This causes the Black Tea Pokémon to drop its tea cap on the floor and its purple liquid to spill out, which Liko and Roy respectively realize came from Polteageist. Shuckle attacks again, and this time, at Cap's urging, Polteageist dodges it, causing Shuckle to crash into the Berry crates behind it. Polteageist wants to keep the battle going, but then looks at all the Pokémon cheering for it, having earned their respect. Polteageist uses Teatime, making music and pouring all of them some of its tea. Looking at Polteageist, Shuckle shoots Berries out of its shell to have with the Black Tea Pokémon's tea. Liko realizes Quaxly was doing this without the rest of the crew ever noticing. Roy wants to join them too, but Liko wants to let the Pokémon have their own private time. After Polteageist and Shuckle come to respect their different tastes, the former shares the Rising Volt Tacklers handshake with Cap. The elated Polteageist spins around and spills its purple liquid, which Fuecoco slips on yet again. Luckily, all the Pokemon are there to catch the Fire Croc Pokémon.
The next day, the Rising Volt Tacklers are gathered outside on the Wing Deck for a meal. Liko and Roy hand out food to the Pokémon belonging to each of the crew before noticing that the rest of the Pokémon are tired from staying up all night. Friede comes over and is not so surprised to see Polteageist among the sleeping Pokémon. The crew tells Liko and Roy not to get so hung up on it, claiming that everything is fine as long as everyone is comfy. Just then, everyone gets startled at Friede suddenly spitting some bad-tasting tea from the antique cup Diana had before, revealed to be a Sinistea. Diana reveals to Liko that that the experiment she was testing last night with her antique teacup involved Polteageist creating this Sinistea from its tea. The crew watches Sinistea drifts off to sleep next to Polteageist.