While our heroes are having lunch on the path to Nimbasa City, a Roggenrola comes crashing down on them, ruining their feast! Ash decides he wants to catch it, so he makes a couple of attempts using Tepig and Oshawott. The Pokémon are unsuccessful, and they end up needing to visit a Pokémon Center. All this time, the Roggenrola seems to be urgently trying to tell them something. However, in a hurry, our heroes ignore the Roggenrola and leave it behind.
It is at the Pokémon Center that we discover its water source, located in a cave, has been mysteriously cut off. Accompanying a representative from the water company named Garrison, our heroes go to the cave to investigate. We discover that it’s Team Rocket who is to blame for blocking the water supply! They’ve also been catching the Roggenrola that live in the cave in order to implement a new weapon Doctor Zager has invented, which concentrates the power of the Roggenrola’s energy core.
Angrily, our Ash and his friends fiercely battle Jessie, James, and Meowth, and soon the Roggenrola are freed. Garrison arranges to have the water supply restored to the Pokémon Center. Ash also discovers the Roggenrola they first encountered wants to go with him. A battle ensues between Roggenrola and Tepig, and this time Tepig prevails. Roggenrola joins the group as Ash’s newest Pokémon friend!
A wild Roggenrola runs out of a cave, panicked, and escaping through a tunnel. Meanwhile, Ash, Iris, and Cilan are having pie which Ash compliments. As Cilan begins to explain how it was made, the Roggenrola jumps out of the tall grass and smashes into the table, destroying the pie, causing Cilan much distress. However the Roggenrola doesn't seem to notice as it begins rambling on. Ash scans it into his Pokédex and then decides to catch it.
First he sends out Oshawott who is ordered to use Water Gun. Its attack is deflected when Roggenrola kicks a bowl in front of itself. Oshawott then tries an Aqua Jet, which Roggenrola evades causing Oshawott to crash into the table and knock himself out. As Roggenrola makes its landing from dodging Oshawott's attack, Cilan notices a strange device on its back. Ash then sends out Tepig and orders him to use Tackle. Roggenrola again dodges the attacks with ease and Ash orders Tepig to use Flame Charge which lands a direct hit and ends up knocking the device off Roggenrola's back. However Roggenrola is still standing due to its Ability. Tepig comes back with another Tackle, but before it can reach Roggenrola, the Mantle Pokémon stops Tepig in his tracks with Sandstorm immediately followed by Stone Edge which knocks out Tepig. Ash then picks up Tepig and hurries to the Pokémon Center, glancing back at the Roggenrola who is still acting strangely.
The trio is then seen waiting in the Pokémon Center lobby when Nurse Joy emerges from the examination room with Tepig and Oshawott's Poké Balls and states that they made a full recovery. As Ash retrieves his Poké Balls, a man enters the room and explained that the equipment at the Pokémon Center is working efficiently. Nurse Joy introduces the man as Mr. Garrison and explains that the Pokémon Center hadn't been receiving water and she hired Mr. Garrison to look into the issue. Mr. Garrison explains that the problem may be caused by the source of the Pokémon Center's water supply: a spring located deep within a cave which then travels through a man-made canal to the center. Intrigued, Ash asks to know more, and Nurse Joy explains that the cave is home to lots of wild Roggenrola. Iris remarks that they saw a Roggenrola earlier, which surprises Mr. Garrison and Nurse Joy, claiming that Roggenrola rarely venture outside of the cave and begin to worry about them. Cilan then points out that he saw a device strapped to the Roggenrola they saw earlier. Convinced, Mr. Garrison decides to go and investigate the cave and agrees to let Ash and co. go along.
The Roggenrola from before is then seen talking to other wild Pokémon in the area before they hear a loud crash coming from the cave. Many Roggenrola are then seen running around maniacally in the cave before being captured by metallic suction cups and pulled into a large, rounded machine. It is revealed to be a vehicle created by Team Rocket after receiving a mission from Dr. Zager. The group then arrives at the cave and realize the canal has been dried up, supporting Mr. Garrison's theory. Roggenrola then appears before Ash and motions for them to follow it into the cave. They are led to a massive rock pile at the mouth of the canal, when Team Rocket's vehicle appears and attempts to capture Roggenrola. After reciting their motto, Team Rocket reveals that they are going to use the Roggenrola to power their latest weapon. Ash has Tepig use Ember to break the metal arm connected to the suction cup, freeing Roggenrola. Team Rocket then settle with one less Roggenrola and retreat behind a rock slide. As some of the rocks begin to fall on top of them, Roggenrola uses Flash Cannon to protect everyone from harm. Team Rocket, now outside the cave, test out their weapon which amplifies the power of the Roggenrola cores and then fired a combined Flash Cannon, causing the exit of the cave to collapse. Satisfied with the device, Team Rocket leave to report back to Dr. Zager.
Trapped, Mr. Garrison begins to contemplate how they'll escape the cave. However, Iris confidently exclaims they have nothing to worry about and sends out her Excadrill and orders it to dig a tunnel out of the cave. Cilan then has Pansage assist Excadrill. Now freed from the cave, Mr. Garrison states that Roggenrola could find the others using its sensitivity to sound, so the four of them rush off to find the others with Roggenrola leading the way. They manage to catch Team Rocket just in time when Jessie sends out Woobat and has it use Gust, when it is then hit by an Ember attack from Tepig. Team Rocket then resort to using their Roggenrola cannon to attack the group. Roggenrola runs in front of the cannon and begs its friends to resist attacking. Its pleas fail and the cannon fires as planned, but it manages to deflect it with a Flash Cannon of its own. The Roggenrola then begins charging another attack, but this time Ash runs in front of them as well, and the Roggenrola manages to resist the influence of the machine, which causes it to malfunction and free all the Roggenrola. Angered, James sends out Yamask and has it use Night Shade combined with a Gust from Woobat. Tepig manages to disable the attacks with Ember, and Pikachu launches an Electro Ball as the wild Roggenrola fire a combined Flash Cannon, forcing Team Rocket to retreat.
With all the Roggenrola safe, the team head back to the Pokémon Center where every one of them is tended to by Nurse Joy along with Pikachu and Tepig. Once they are cared for, Mr. Garrison informs everyone that his company will take care of the issues in the cave immediately, as well as restore the Roggenrola's home to its prime condition. Overjoyed, the Roggenrola that spent the day with Ash then requests that he follow it outside where it then makes a stance in the field as it if wanted to battle. Cilan explains that Roggenrola wants to accompany Ash on his journey, an offer that Ash happily accepts.
Ash sends out Tepig to battle Roggenrola once more, much to Iris's surprise who stated that Tepig had already lost against Roggenrola earlier, and the fact that he has a type-disadvantage. Ash however feels it's all the more reason to challenge Roggenrola again with Tepig. He starts off having Tepig use Tackle which is immediately countered by Roggenrola's Sandstorm and Stone Edge combination. Roggenrola then begins charging Flash Cannon when Tepig charges into it with Flame Charge, which causes a minor explosion. Tepig attacks with a Tackle which Roggenrola absorbs. Roggenrola continues to absorb his Tackle attack until he manages to land a critical hit on Roggenrola, sending them both toppling over. Ash then throws a Poké Ball that catches Roggenrola and locks it inside, officially adding the Roggenrola to his team.