After a practice battle between Ash's Chimchar and Dawn's Piplup, Chimchar begins to cry because Ash was nice to it even though it lost, and Paul wasn't. Things get worse when a trio of Zangoose attack and Chimchar has to face its fear and eventually defeats them and overcomes its fear of Zangoose. Chimchar also receives some unexpected advice from Meowth about the future.

Gardenia reappears in a town, organizing a special exhibition battle for the town's children. She teams herself with James of Team Rocket in a match against Ash and Dawn. She proposes that James should leave his Cacnea with her to train when he is unable to use it to its full potential. He eventually decides to accept the offer.

Buizel is more interested in Ash's gym training, and Aipom is more interested in Dawn's contest training. Thus, Zoey suggests that Ash and Dawn do a trade.

After Ash's Buizel destroys the Hallowed Tower, a Spiritomb is unleashed and attacks Ash, Dawn, Brock and a nearby village. Then Jessie tells it that Ash is a descendant of the Aura Guardian that coincidentally has a Pikachu, that sealed it away. So Ash sets out to stop the Spiritomb and with Pikachu's help, they seal it away in the Hallowed Tower.

Ash's group encounters a Pokémon Breeder working on the construction of a stone bridge. The woman is arguing with the bridge's designer because of their Pokémon assistant Bibarel's refusal to work. After the stone cutter returns, Bibarel begins to construct the bridge, with help from the gang.

Ash battles Alan, a trainer that wants his Nosepass to evolve into a Probopass, but it can only evolve if it levels up in Mt. Coronet. When it does, Team Rocket brainwashes it and now Ash & Co. have to get it back.

Ash encounter a young Officer Jenny named Marble and her Luxray. Luxray is unable to use its electric moves, so Ash & Co. set out to help it.

In Solaceon Town, Ash's group meets up with Dawn's old friend and rival Kenny and his new Pokémon, Breloom. Kenny tells them he is going to the Solaceon Ruins, a place of worship for the legendary Dialga and Palkia, so they tag along, only to get more than they bargained for when the Unown that live in the ruins become furious along with the appearance of the sinister Team Galactic. Among the chaos, Aipom evolves into Ambipom

Dawn competes against Kenny in the Solaceon Town Contest, looking for redemption after her crushing loss in Hearthome City. Jessie of course enters. Dawn loses once again and Kenny and Jessie face-off in the finals. Jessie defeats Kenny and wins her first ribbon. Zoey tells Dawn that the overuse of Swift caused Ambipom to be no longer seen and the point of an Appeal is to show off the Pokémon.

On their way to Veilstone City, Ash and his friends stop off at the Mountain Hut Maid Café for a nice drink of Miltank's Milk. However, when they arrive, they learn of the troubles the Café is having, being under-staffed. Ash and his friends offer their services and soon become Maids in the Café. Brock helps Autumn, the youngest of three sisters bond with her Miltank, Ilta. All the while Dawn is trying deal with her feelings of losing a contest for a second time.

Ash and his friends stop at a Hot Spring managed by Dawn's childhood friend, Leona. Both girls are happy to meet again, but when Dawn and her friends want to go to the hot springs, they find out that there isn't any water. Because no water is coming from the spring, the group want to investigate, along with Leona and her Swinub.

Ash and company visit a town where it is plagued with a group of Gligar led by a Gliscor. Ash and friends help Officer Jenny try to remove the flying Pokémon, while Ash's rival Paul sets his eyes on capturing Gliscor. In the end, Paul captures the Gliscor on his team, and Ash captures one of the Gligar that keeps showing up.

When our heroes' Pokémon are having a fun time in a sandpit, a Hippowdon appears from within. However, the over-curious Pachirisu can't help peeping into the Hippowdon's mouth and accidentally falls into it. The situation gets worse when Hippowdon becomes the target of the Team Rocket duo Butch and Cassidy.

In the forest just outside Veilstone City, the group witness a young female martial-artist and a Lucario in a fierce battle. The girl is revealed to be Maylene, the city's Gym Leader, at which point Ash immediately asks for a Gym Battle. However, she recently lost to Ash's rival Paul, and is depressed over her defeat. Further insight into the matter is revealed by Reggie, Paul's older brother. Reggie also helps Ash's Staravia learn Brave Bird.

Dawn challenges the gym leader of Veilstone City, Maylene, in hopes of helping Maylene get over her defeat. Maylene defeats Dawn and she and her Lucario regain their confidence.

Maylene finally accepts Ash's challenge. Ash uses Staravia, Chimchar, and Buizel against Machoke, Meditite, and Lucario. The battle between Buizel and Lucario ends up in a tie but Maylene still gives Ash the Cobble Badge.

With Ash acquiring the Cobble Badge, our heroes decide to spend the night in Veilstone City before heading out. Reggie takes the group to a park with several meteoric stones lie. However, Team Galactic appears and try to steal them for their world domination plans.

While training Gligar, Ash hears singing. When they look to see who is singing, they meet a magician named Francesca and her three Chingling. Francesca is trying to get her spoiled Chingling to have a better attitude.

On their travels, Ash and his friends meet up with another Pokémon Ranger—Kellyn—and a Riolu. It turns out that Hunter J is after Riolu, due to its ability to use Aura Sphere before evolving. Ash and Riolu start to bond with their shared Aura, but J is insistent on getting it. This episode relates to the secret mission in Pokémon Ranger: Shadows of Almia, from which the player can transfer a Riolu that knows Aura Sphere to their copy of Diamond, Pearl, or Platinum.

Hunter J has managed to kidnap Riolu. But despite that, Riolu, reveals his whereabouts to Ash, using its Aura. With Rangers Kellyn and Solana joining them, Ash and his friends go to hunt down Hunter J and get Riolu back. However, J is far more formidable than anyone could have anticipated. Will Ash and friends be able to return Riolu back to its kingdom?

Ash and Co. arrive at a lakeside Pokémon Center. Jessie's Dustox sees a shiny Dustox, and follows it to the lake. Jessie releases her Dustox, allowing it to mate. This is related to the Season 1 episode 21, "Bye Bye Butterfree" where Ash releases his Butterfree so it can mate with a pink Butterfree.

Ash and his friends meet Sho, a boy who has a Pichu and a Raichu. He mistakes Ash's Pikachu for a wild Pokémon. Just like at the Vermillion City Gym, Ash and Pikachu have the option again to evolve Pikachu to Raichu, after a loss to a stronger opponent. Paul witnesses this defeat and scolds Ash for losing to such an opponent, but manages to redeem himself of that defeat in a rematch.

Ash, Brock and Dawn meet the Champion of the Hoenn Region, Wallace. He says he will be holding a Pokémon Contest and the winner receives a ribbon that can be used anywhere. The group spends the day with him, resulting in advice from Wallace for Dawn to play with her Pokémon more and for Ash to enter Buizel in the contest. At the end of the episode, Ash receives a phone call from his friend, May.

Ash and Brock's old friend May, still training to become a Top Coordinator, visits Sinnoh for the Wallace Cup. Upon arrival at the Seven Stars Restaurant, they find out that only those who win a tag-battle against the restaurant's owners can eat there. Ash partners with Brock and win the double combat with a single move. Before Dawn and May's combat, Team Rockets steals all food from the restaurant. May and Dawn partner up and defeat both the Team Rocket and the restaurant's owners, the later by using Blaziken and Piplup together to create a fantastic fire/water combination. There is a cameo from Drew, Harley, and Max.

Ash and his friends have arrived at the Lake Resort where the Wallace Cup will take place. Zoey also arrives, and competes, too. Right when the contest began, Dawn becomes nervous and has trouble keeping her composure. Meanwhile, May decides to enter with Wartortle, and Ash enters with Buizel. There are cameos of Drew, Harley, Max, Norman, Caroline, and Solidad.

At night, Ash takes a walk near the Lake Valor with Pikachu when suddenly, something in the center of the lake begins to glow, and it turns out that Azelf appears. When Ash tries to approach it, the shadow disappears again. The next day, the second round of the Wallace Cup begins. May's Venusaur is then revealed, and there is a cameo appearance of May's Skitty battling in the second round. Dawn, May and Zoey make it to the semi finals but Ash loses to a tough coordinator called Kyle. After it is Dawn's turn to battle Kyle in the semi-final, she uses Piplup against his Crawdaunt. There are cameos of Norman, Caroline, Max, Kenny and Paul.

Dawn beats Kyle and May beats Zoey in the semi finals and both have to battle in the finals. In the finals, Dawn faces-off against May in the Wallace Cup. Dawn uses Piplup and May uses her Glaceon. Dawn manages to narrowly defeat May's Glaceon by a fraction. After the contest ends, Dawn earns her second Ribbon! Now that the contest is over, May departs from Ash, Dawn, and Brock once again and goes back to Johto.

When on their way to Pastoria City, Ash and friends meet a trainer named Tyler that wants to catch a Yanma. But Team Rocket ends up catching it after he weakened it. After Jessie captures the Yanma and sends it to Giovanni, who rejects it, she decides to train it herself and it quickly evolves into Yanmega.

Ash and co. are running after Gligar who has been blown away by a gust, and promptly run into Paul. After a huge argument about their different ways of treating Pokémon, Ash challenges Paul to a battle. But when Chimchar is battling Paul's Ursaring, it activates an overpowering blaze. Chimchar also gets confused and starts randomly attacking anyone in its path.

After Ash & Co. arrive in Pastoria City, Crasher Wake refuses Ash's request for a battle because he has to take care of something. They tag along and find out there is a Croagunk Festival in the Pastoria Great Marsh.