Ash, his friends, Brawly, and his apprentice Shauna make their way down a winding rocky path, towards an island where the rematch for the Knuckle Badge would be held at. Meanwhile, Team Rocket somehow manages to fall into Brawly's sparring area and begins to raid his fridge, stuffing all they can into their mouths. It isn't long before they're found by Brawly and the group, however, but they proclaim the place to be their new secret base, and they're prepared to battle for it. Jessie sends out her Seviper and James calls on his Cacnea. Seviper blinds the group with a Haze attack while Cacnea shoots through it with Pin Missile, barely missing Ash and Pikachu. Ash is prepared to fight back, but Brawly tells him not to and warns Team Rocket to leave. They decline, but soon regret their choice as a deep rumbling is heard beneath them, and a geyser blasts them through the very hole they fell into. Brawly tells the group that geysers like that one are caused by the shape of the island, and some waves that hit it cause jets of water to shoot up into the air through holes like that one.
Later on, Brawly shows everyone his sparring area, which has a plethora of machines that are capable of training many different kinds of Pokémon. They then make their way to the battlefield, which is a gigantic rectangular slate surrounded by a narrow moat littered with stalagmites. On the battlefield itself are several gaping holes, each a passageway for a geyser of its own; in the center, there is a painted circle to warn challengers of such occurrences. The room is lit brightly by six suspending spotlights attached at different points on the cave walls. Ash tells Pikachu to sit this one out, since he has a new strategy to try. Max is doubtful, but Brock tells him to just relax and enjoy the show. Shauna, acting as the referee, tells the two combatants that this is a two-on-two Pokémon battle, and only the challenger is allowed to substitute.
Brawly wastes no time and sends out his Machop while Ash calls out Treecko, whom shakes its tail readily at the opposing Pokémon. Machop begins with a speedy Karate Chop, which slices through a nearby stalagmite as Treecko nimbly dodges the attack, landing nearby on another rock formation. Machop attempts another Karate Chop attack, but Treecko evades it once more, leaping from rock-to-rock as easily as if they were the familiar trees of home. Machop becomes annoyed and sends three more Karate Chop attacks at Treecko, only to be easily avoided by the small Wood Gecko Pokémon again and again. Brawly orders Machop to use Cross Chop, but the move fails, leaving it vulnerable. Treecko uses the opportunity to smash into it with a Quick Attack, sending it flying backwards into the battlefield. Just when Ash thought the opposing Pokémon was done for, Brawly reminds him about the geysers and grins confidently. The ground begins to rumble and Machop readies another Cross Chop, positioning itself over one of the holes. A jet of water shoots up and propels the Pokémon at Treecko, but just before the impact, Ash recalls it.
His next Pokémon to go is Corphish, who, with a combination of Bubble Beam and two Crabhammers, knocks Machop out of the battle. Next up is Brawly's formidable Hariyama. Immediately, it springs into action with several Arm Thrusts. Ash quickly tells Corphish to use Harden, in hopes that the bigger Pokémon will get tired as it keeps up the onslaught. This theory is quickly proven wrong, as Hariyama doesn't slow down in the slightest, and Ash instead orders Corphish to jump into the water. Hariyama follows, landing on a sturdy flat rock in the moat as it began the search for its foe. Ash knows Hariyama is a good surfer, but it's too big and heavy to move easily through the water like Corphish. Corphish quickly springs from the water, smacks Hariyama with a Crabhammer attack, and retreats back into the depths. Brawly, seeing this as a potential problem, orders his Pokémon to use Arm Thrust at the water, which brings Corphish back up. It then grabs the crustacean and swirled into a Seismic Toss, thrusting it into the hard rock below and knocking it out.
Ash recalls Corphish thanking it for battling. He then takes out Treecko's Poké Ball and right before sending it out, he remembers they lost to Brawly and his Hariyama due to his recklessness. This time they won't lose against them. Ash calls out Treecko to the plate who is ready for a rematch against Hariyama. Hariyama starts the battle by quickly rushing forward with an Arm Thrust. Treecko dodges it and delivers a strong Pound to Hariyama's right leg before jumping back to evade another Arm Thrust. As Hariyama keeps up the offensive with several more Arm Thrusts, Treecko manages to dodge each one, landing a few more Pound attacks on Hariyama's legs while carefully keeping its distance. Brawly orders his Pokémon to settle it with Vital Throw, but the pain shooting through its legs slows it down, and the attack misses Treecko by mere inches.
At this point, both Pokémon are exhausted. Ash picks up on the sudden rumbling of water beneath them and announces that this will be the deciding point in the match. Brawly agrees, and both of their Pokémon position themselves over separate parallel holes, awaiting the right moment. As the geysers spring forth and propel them at one another, Hariyama readies its Knock Off attack while Treecko spins in preparation for Pound. Both attacks make contact and the two pass each other, landing on opposite sides of the battlefield. Each spectator waits in agonizing anticipation as neither of the Pokémon move a muscle. After a long moment of silence, Hariyama falls unconscious and Shauna declares Ash the winner of the match! Ash cheers and praises Treecko, and the group heads back outside. Outside, just as the sun set on the horizon, Ash receives his Knuckle Badge from Brawly; his proof of winning his second Gym match was now shining in his hands, and he declared it to the sky. Brawly tells him that if he always keeps his focus and keeps on striving with a cool head, he'll be a force to reckon with in the Hoenn League. With Brawly's words of advice still fresh in his mind, Ash and his friends set out once again for their next destination.