Ash and his friends run into Gardenia, the Eterna Gym Leader, in the middle of her travels through Sinnoh. Gardenia is about to show off Pokémon battling with a friendly match, but Team Rocket interrupts to try and steal Pikachu! Of course, the minute Gardenia sees James' Cacnea, her love for Grass-type Pokémon blinds her to everything else, and suddenly James finds himself joining Gardenia in a tag battle against Ash and Dawn. Acting on Gardenia's advice, James has Cacnea try a new move, Drain Punch, but it only works once before Pachirisu and Aipom win the battle.

James turns down Gardenia's offer to train Cacnea, but it's still on his mind as he and Cacnea train hard to perfect this new move. Jessie and Meowth convince Ash and his friends to help Cacnea train, too! Dawn is understandably skeptical about helping Team Rocket power up, although Drain Punch still doesn't work even after Ash and his Pokémon help Cacnea train.

Gardenia returns in the middle of Cacnea's training battle against Ash's Aipom. Even though Cacnea battles with every last bit of its strength and beyond, it still can't pull off Drain Punch. Remorsefully realizing that he's just not skilled enough to bring out Cacnea's full potential, James stops the battle and tells Cacnea to go with Gardenia. He bids a tearful farewell to his Pokémon before running off, followed by Jessie and Meowth. But wherever he goes, James won't forget Cacnea and all their times together!