On the way to Fennel Valley, Ash's Aipom scampers away and runs into a Weavile with an attitude. Aipom's up for a battle, but Weavile deals it a harsh defeat! Luckily, Ash and his friends meet a passing wilderness guardian named Kerrigan, who lets Aipom rest at his home. Kerrigan explains that the Weavile belonged to a local group of Weavile and Sneasel, but now it's alone and challenges any Trainer's Pokémon it sees. Ash resolves to help Kerrigan find the stray Weavile before anyone else is hurt.
Team Rocket wants to find Weavile, but once they do, it's not interested in joining their gang. Ash and his friends can't seem to get through to the Weavile, either. Then a Sneasel shows up on the scene, and the truth comes out! The stray Weavile was leader of the Weavile and Sneasel group, until another Weavile came and beat it in a battle for leadership. However, the new leader turned out to be a bully, and so Sneasel left the group as well.
That's when the Weavile leader shows up to bring Sneasel back. Ash challenges the stray Weavile to stand up for itself and help Sneasel, and both Weavile decide to battle. The stray Weavile comes out the winner and becomes leader once again. The losing Pokémon won't be left out in the cold this time, because Sneasel asks both Weavile to cooperate with each other—and they agree! Now the forest will once again be at peace, and our heroes can continue their journey to Ash's rematch with Brandon!
While heading towards the Battle Pyramid for Ash's final Frontier challenge, the group takes a break in a forest clearing. Aipom, interested in the flowers, wanders off and gets lost, coming face-to-face with a wild Weavile. Weavile challenges Aipom to a battle, starting with Shadow Ball; the explosion alerts the group that Aipom is in trouble. Rushing over, May scans the Weavile with her Pokédex. Ash asks if the Weavile wants to battle, to which it replies with another Shadow Ball. The gang quickly moves out of harm's way, only to be attacked by another Shadow Ball. Ash has Pikachu use Thunderbolt, though Weavile evades and replies with another Shadow Ball. Pikachu attempts to dodge, but gets caught in the crossfire. Aipom quickly covers for Pikachu, although Weavile dodges her Swift attack. Ash tells Aipom to use Double Team, followed by Swift. Still, Weavile is able to dodge and goes straight into a Shadow Ball attack, hurting Aipom and knocking her out. While Weavile leaves the scene, Jessie of Team Rocket hopes to add the aggressive Pokémon to her team. Meowth advises against it, and soon leaves to fight Weavile on his own.
Looking up after helping Aipom, the group notices Weavile has disappeared. Soon enough Kerrigan, a member of the Wilderness Guard Corps, invites the group to his base to help Aipom recover. Once inside the small cabin, the group inquires about the Weavile. Kerrigan says the Weavile is a stray and that there is a gang of both Weavile and Sneasel. He claims that Weavile had left the group and now challenges random Trainers to battle it. Kerrigan decides it would be best if he went outside and searched around. The group decides to tag along, leaving Aipom to rest after her harsh battle. Kerrigan leads them to a forest location, which Weavile is known to frequent. However, Weavile isn't there, so Max suggests Pikachu track it down using its scent.
Meanwhile, the stray Weavile glumly looks at its reflection in the river. Jessie and James watch as Meowth approaches it, dressed as a fellow Weavile. Weavile, however, doesn't seem to buy that Meowth is a fellow Weavile at all, even smacking away Meowth's hand to avoid a handshake. After Weavile threatens him, Meowth flees to the safety of his teammates. Jessie, unsatisfied with Meowth's claims, angrily threatens to do worse to Meowth if he doesn't get out and talk to Weavile. Before Meowth can react, Ash and friends show up. Pikachu runs over to Weavile and begins to talk to it. Meowth translates for Jessie and James, saying that Pikachu asked what Weavile was doing, to which Weavile replied that it didn't need to answer that question. After that, Meowth couldn't follow. Jessie angrily stands up, yelling at Meowth and revealing their position to the twerps. After their motto, Jessie throws herself at Weavile's feet.
Soon, a Sneasel runs over, happy to see the stray Weavile. Meowth begins to translate their conversation. Weavile asks the Sneasel why she had followed it, to which Sneasel replies that she wasn't following the Weavile, she was escaping from the rogue Weavile that the stray Weavile had fought with for leadership. However, Weavile had lost the match, ending up with a scar on its face, and also becoming a stray. Weavile explains that its motives behind attacking the random Trainers was to be tough. The female Sneasel reveals she was sick of being pushed around by the rogue Weavile, which turned out to be extremely mean, so she ran away from the group. Immediately following the speech, the rogue Weavile shows up, with three other Weavile as backup. Sneasel cowers behind the stray Weavile, to which Jessie responds that the Weavile was hers. Weavile, angered by her, easily sends Team Rocket blasting off with a Shadow Ball.
Soon, the battle between the four Weavile and the stray Weavile ensues. The three Weavile attack first, but are in turn attacked by Pikachu. The rogue Weavile angrily attacks the stray, beginning a one-on-one battle with both Weavile running along the river bank. The rogue uses Shadow Ball which is easily dodged by the stray, who also uses Shadow Ball. The stray's Shadow Ball hits the water, splashing it up between the two. The rogue Weavile jumps through the water and tries to slash Weavile's face with its claws. Weavile is able to block the attack with its own claws and send the rogue Weavile flying into the water, following up with a Shadow Ball. Unfortunately, the other Weavile is able to escape, using Shadow Ball on the stray one. The stray Weavile remembers its previous battle with the rogue Weavile and realises it was planning on using the Shadow Ball as a distraction to slash at its face like before. Weavile dodges the oncoming Shadow Ball and is able to use its claws to throw the rogue away. Almost defeated, the rogue Weavile lands beside the riverbank. The stray jumps on top of it and thrusts its claws at it. The rogue braces itself, but no attack comes. Sparing the rogue Weavile, the stray has now regained its place as the leader. Both the new leader and the rogue Weavile made a truce, with Sneasel's help. After thanking Ash, Weavile walks off in peace to go back to its group with Sneasel and the others.
Ash and his friends head back to the cabin, finding a fully recovered Aipom. With their work done, the group says goodbye to Kerrigan. Aipom happily runs on ahead, setting the pace for everyone else to catch up as they journey towards the Battle Pyramid.