As our heroes make their way up a rocky hill, an unconscious Goomy falls out of the sky, right onto Ash's head! Clemont figures out that Goomy isn't feeling well because it's dehydrated, so Ash braves a steep climb to get it to the nearby river. But as soon as it's restored to health, Team Rocket swoops in to grab Pikachu, and Goomy ends up in their cage as well!
While Jessie, James, and Meowth are celebrating their latest catch, the two Pokémon are working together, combining Pikachu's strength and Goomy's slime to escape the cage and flee. When they reunite with Ash and the others, Team Rocket is close behind!
The villains seem to have the upper hand until Goomy steps in front of its new friends and uses Bide, absorbing Team Rocket's attacks and then blasting them off with their own power. Ash admires Goomy's unexpected strength, and the little Dragon-type Pokémon happily joins him for the journey to Coumarine City!
Continuing towards Coumarine City, Ash and his friends are quickly tiring from the mountainous route. The group soon notices a Swanna flying overhead, before dropping something directly onto Ash's head. Ash pulls the particularly slimy object off his head. Bonnie starts poking at the object, while Ash pulls out his Pokédex which reveals that they have encountered a Goomy, which is considered to be the weakest Dragon-type Pokémon. Noticing Goomy’s extremely weak and flattened appearance, Clemont remarks that Goomy are mostly made up of water. So, Serena takes out a bottle from her bag and pours water onto it. Goomy then awakens weakly to find itself surrounded by Ash and his crew. Ash wants to help Goomy make a full recovery, and he soon spots a nearby river somewhere downhill. He grabs Goomy and makes the steep descent, but the terrain proves so rough that Ash runs down quickly and uncontrollably. Though Ash is able to dodge most obstacles, he trips over a rock, causing Goomy to be thrown into the air. However, he grabs it in time, only to crash into the river below.
Serena and the others soon join Ash in the river, where they pour water over Goomy to help it recover from its dehydration. Goomy gives everyone a large smile to assure everyone that is it feeling much better. Soon Dedenne pops out of her bag, but this causes Goomy to leap onto Ash’s head for safety. Clemont theorizes that because the Dragon-type is weak against the Fairy type, Goomy is scared of Dedenne. Bonnie then calls Goomy weird for being scared of a cute Dedenne. Goomy, offended by her remark, hits her legs with its horns, but Bonnie laughs as the assault is just tickling her. Serena then suggests that the remark must have insulted Goomy, and Goomy happily approaches Serena's ear and nibbles it, which suggests that she must have been right. However, Serena says that Goomy feels somewhat gross and slimy, causing Goomy to fall back into the river. It then uses Rain Dance on Serena in its displeasure. The sudden downpour stops immediately after Serena apologizes. However, Goomy soon quickly becomes upset once more, and Ash realizes must be hungry now. Goomy immediately leaves the river, leading everyone into the forest to search for food. Meanwhile, Team Rocket is spying on the twerps. They consider capturing Goomy, but decide such a weak Pokémon would be completely worthless, and they should stick to capturing Pikachu.
Back to the group, they watch Goomy eating leaves from a bush, clearly enjoying its meal. Chespin suddenly pops out of its Poké Ball and uses Pin Missile to knock down some apples from the tree. However, an angry Ariados arrives on the scene, causing Goomy to hide in fear behind Pikachu. Pikachu blocks Ariados from attacking before Clemont and Chespin apologize, telling Ariados they meant no harm. Ariados then leaves, while Goomy is visibly scared. Ash assures Goomy it's all over, but it is still extremely terrified, shivering with fear while a large amount of water leaks from its body. Clemont then devises a large device that can scan images in a Pokémon's brain and visualize them, calling it the "Pokémon Translator Mark 2." As he scans Goomy, the screen reveals Goomy’s homeland was attacked by a swarm of Bug types. A flock of Swanna took to the skies to escape the ambush. The machine, however, then ceases to work. Clemont hits it three times, but the machine self-destructs, to which Bonnie remarks she is not surprised. Clemont theorizes from the video that Goomy was caught in a large Pokémon skirmish and fled. Goomy chews Clemont's ear in approval, and soon enough Serena's as well when she states that it must be the reason for Goomy's fear of Ariados. It then speaks to Pikachu, but their conversation is incomprehensible to Ash and his friends.
Suddenly, a device falls from the sky, entrapping the group in an electronic rope. It turns out that the culprit was Team Rocket, who proceeds with their motto while floating in their balloon. Ash tells Pikachu to use Thunderbolt, but the Team Rocket’s balloon net attachment easily absorbs the voltage before trapping Pikachu and Goomy. With a smoke bomb, Team Rocket then escapes with their catches. Ash calls out Frogadier to cut the restraints before having Fletchinder search for the Rocket trio.
Having landed, Team Rocket watches in glee as Pikachu uses Thunderbolt on the cage repeatedly. Just then, they notice that they've taken Goomy as well, and figure there's no harm in taking another Pokémon. With their captures safely secured, the trio decides to have a forest picnic before they deliver the Pokémon to the boss. Meanwhile, Pikachu continues trying to use Thunderbolt on the cage, but his attempts are all in vain. Next, Pikachu turns to hit the cage in the same spot with his head. Pikachu successfully opens the cage up a bit and manages to push Goomy out of the gap. However, Pikachu then finds himself unable to squeeze through. Goomy then re-enters the cage and proceeds to slides itself all over Pikachu, causing Pikachu to have a shiny glow. Before they can leave the cage, however, Team Rocket approaches them, having heard a loud clang. They ask if Pikachu and Goomy have been trying to escape, and the two Pokémon just cover the enlarged hole, smiling innocently. Meowth wonders if Pikachu has always been this glossy, so Pikachu and Goomy try to mask it as extreme sweat. Team Rocket assumes that it was nothing, and resumes their party. The trio note that Pikachu was particularly glossy, and the three realize it would be a perfect trick to slip through the cage bars. As they rush to check the cage, Team Rocket spots their escapees, with Pikachu running away while carrying Goomy on his back. James runs after them, while the others decide to use the Meowth balloon. Fletchinder soon spots Team Rocket pursuing Pikachu and Goomy, and returns to inform Ash and the others.
James quickly catches up to Pikachu and Goomy, but before he can reach them, Goomy uses Rain Rance above James's head, causing him to slip and start rolling over. The others in the Meowth balloon catch up to James, and he climbs into the balloon. Jessie sends out her Pumpkaboo and commands it to use Shadow Ball, but Ash arrives in time and uses his body to block the attack from hitting. The rest of his friends catch up, but Team Rocket traps them in a rope again, narrowly missing Ash. Team Rocket takes out the same electricity-absorbing mecha from before, and Ash has Pikachu use Iron Tail on it, successfully breaking it. James then sends out his Inkay and has it use Tackle while Jessie's Pumpkaboo uses Shadow Ball. Ash's Fletchinder counters with Peck and Pikachu counters with Electro Ball. However, when Inkay uses Psybeam on Pikachu and Fletchinder, the attack manages to confuse both Pokémon. Pumpkaboo uses Dark Pulse while Inkay uses Psybeam, but before the attacks can hit Ash, Goomy steps out in front of him and endures the attacks. When Jessie and James command their Pokémon to attack again, Goomy endures the attacks once more. Goomy then retaliates with Bide, and just then, Pikachu and Fletchinder snap out of their confusion. Pumpkaboo launches another Shadow Ball, but Pikachu strikes back with Thunderbolt, sending Team Rocket blasting off.
Afterward, Ash compliments Goomy on its powerful performance against Team Rocket. Goomy blushes, and Dedenne cheers in agreement with Ash. However, Goomy still appears to be scared of Dedenne and hides behind Pikachu while shivering in fear. Clemont suggests that there is probably a deeper reason for Goomy's fear. Pikachu and Goomy talk to each other, and Pikachu excitedly tries to tell Ash something. Ash asks Goomy if it wants to become strong like Pikachu, to which Goomy jumps up onto Ash's shoulder and nuzzles Ash's head in agreement. With that, Ash successfully catches Goomy. He proceeds to send out his newly-captured Goomy, and he and his friends all welcome Goomy to the group.