Ash and company are finally at the Mauville Gym. They have an electrifying introduction to Wattson, the Gym's leader, who specializes in Electric-type Pokémon. They discover that he seems to enjoy being a bit of a trickster. Upon entering the gym, they are sent through a type of electric slide/roller coaster ending in a mechanical Raikou, which Pikachu tries to attack.
Elsewhere, Team Rocket is exploring the possibility of capturing a large array of Electric-type Pokémon they just found.
Wattson decides on a three-on-three match. He uses his Magnemite, but Pikachu knocks it out in one hit. Next he sends in Voltorb, which Pikachu also KO's in one hit. Finally, Wattson sends in Magneton, which also falls to Pikachu. Everyone is shocked and amazed, but Wattson recovers and hands Ash the Dynamo Badge.
Ash then rushes his Pikachu to the Pokémon Center to recover. There he finds out that it is overloaded with electricity; probably from the Raikou incident. Wattson decides to go to the mountainside to mull over his loss for a bit when he encounters Team Rocket stealing the Electric-type Pokémon. Ash and company arrive and they all help Wattson recover the Pokémon from Team Rocket before sending them blasting off again.
Ash tries to give the Dynamo Badge back to Wattson because Pikachu won due to its being overcharged. Wattson tells him to keep it, though, because Ash deserves it.