The episode begins as usual with Ash, Dawn and Brock on their way to the next Gym so Ash can compete for his third Gym Badge. We find our heroes walking down a barren road, surronded by dying trees and poor plant life. They soon come across a large, uninhabited area much like a small desert, which excites both Ash and Dawn. Ash slides down the slope in front of him and lands on the ground below, before releasing his Pokemon to enjoy the wide open space. Staravia, Turtwig, Chimchar, Buizel and his newly caught Gligar all pop out, and start playing around in the sand. Dawn thinks this is a good idea also, and releases her three Pokemon out as well, as does Brock. The group's enjoyment is soon interrupted however by a loud rumble and the shaking of the ground below them. Instead of the usual Team Rocket however, a large Pokemon bursts out of the ground and roars out of its large mouth. Ash is shocked, and Brock identifies the Pokemon as Hippowdon. Parachisu, who is enjoying itself sitting on Hippowdon's back, runs about on top of its body investigating. It then runs up its head and hangs upside down to look at the large Pokemon's gaping mouth. Dawn warns the Pokemon to get away from its mouth, but it's too late as it then falls right into Hippowdon's mouth which then shuts tight leaving Parachisu trapped! Hippowdon then starts burrowing underground and before the group can react, Hippowdon is gone along with Parachisu! Ash and Brock try digging underground, but are stopped when Pikachu starts calling over having seen something. Not far off, Hippowdon has re-emerged on the surface with Parachisu popping outside one of the crater like holes in its body. Dawn tells her Pokemon to jump out, but Parachisu appears to be stuck. Hippowdon then digs deep underground again leaving the group alone once again.

Elsewhere, Team Rocket are attempting to dig a hole to trap Ash, Dawn and Brock in. They aren't having much luck however, as the sands just keeps on filling in the hole over and over. James complains that they aren't getting anywhere, just as Hippowdon re-emerges again, but as luck would have it, right under Team Rocket causing them to go flying. Team, Rocket land, but before attempting to get up, they spot Ash, Dawn and Brock running towards Hippowdon. Dawn tells Parachisu, still stuck, to use an electric attack to try and set itself free but the attack has no effect on Hippowdon. Brock points out that Hippowdon is a Ground type and thus Electric attacks will have no effect. Hippowdon doesn't seem to notice or care about the attacks, and just burrows underground again. Jessie is amazed, and asks what that Pokemon is. James starts leafing through his Pokemon Trading Cards and finds Hippowdon's card and reads a small description. Jessie jumps up in happiness, saying that if they get that Pokemon, they'll be unstoppable. Meowth agrees, saying that Pikachu's Thunderbolt wouldn't even phase them if they had that Pokemon on their side.

Back with the group, we find them looking around for Hippowdon. Suddenly, Hippopotas emerges from the sand, the same one that the group had encountered before when it was stuck and needed help. Before they can get properly reacquainted, Hippowdon appears out of the sand once again. Hippopotas attempts to greet Hippowdon, as Parachisu appears out of the large Pokemon's nose. However, yet again Hippowdon isn't interested and simply digs underground. Brock tells Ash that Hippowdon evolves from Hippopotas, and Ash asks the young Pokemon if this is so. Hippopotas nods bashfully, and Ash plops the hippo Pokemon on his head thinking that this fact may help them. Not far away, Team Rocket are standing in a tree, also looking for Hippowdon. They spot the Pokemon coming out of the sand again, and James quickly whips out a bazooka that fires a net that covers the entire Pokemon's body. Hippowdon isn't happy about being trapped, and stomps about angrily, trying to get free. Team Rocket then run over to the captured Pokemon but soon realize that it is too heavy and large to simply steal like they would any other Pokemon. At this point, Ash, Dawn and Brock run over shouting at the three to stop. Suddenly the ground below starts to shake and everyone wonders what it could be, especially since Hippowdon is trapped in a net. Something incredibly large emerges from the ground, and when the dust clears a large Rhyhorn mecha is standing before them with a large 'R' on the side.

Ash and Team Rocket are shocked, but their questions are soon answered when the roof of the mecha opens up and two familiar faces appear out of the machine. One is a slim, golden blond haired woman with large triangular earrings clad in a tight black Team Rocket uniform. The other, with teal colored hair with a similar hairstyle to the female, also clad in a black Team Rocket uniform. Ash and Jessie realize who the two are, Cassidy and Butch, both enemies of the two groups. Cassidy isn't happy to see them either, and Jessie shouts at her, asking what she's doing there. Cassidy tells them that they're on a mission for Professor Sanba. At that, Cassidy's phone starts to ring. Cassidy picks up, and an angry Professor Nanba shouts that she got his name wrong. Not bothered, Cassidy tells them that they'll be going now. The two Team Rocket groups start bickering, with both Jessie and Butch getting Nanba's name wrong, and Nanba shouting at them over the phone twice correcting them. Ash, ignoring the two arguing factions, sends out Turtwig to release the captured Hippowdon with its Razor Leaf. The leaf attack breaks the netting trapping the hippo, who proceeds to dig underground again. Cassidy shouts to Botch to get moving, and Butch snaps back, telling her to get his name right. The two then jump back inside their mecha and chase after the escaping Hippowdon.

Not long after, Ash, Dawn and Brock are wandering around the barren landscape looking for the runaway Pokemon. Brock hears the roar of Hippowdon from afar, and the group run after the sound of its roars. Hippowdon is casually walking through the sand, as Parachisu struggles to get free of its stomach. Parachisu spots Butch and Cassidy's Rhyhorn mecha however, and starts shouting at Hippowdon to run. Cassidy from inside the mecha tells Butch to catch it, and Butch hits a button that sends out a long grabbing claw to snatch Hippowdon. Pikachu's Thunderbolt stops the claw however, as the group arrive on the scene and tell Butch and Cassidy to stop. Pikachu attempts to Thunderbolt the mecha itself but Cassidy laughs as the attack phases out on the mecha's armor. Butch smiles saying it's useless. Brock tells Ash they better try and get away, and Ash tells Hippopotas to try and lure Hippowdon away. The group start running and thankfully thanks to Hippopotas's cries, Hippowdon follows. Butch and Cassidy follow, but both parties are soon stopped when the ground beneath them starts to fall away and the group, Hippowdon and Butch and Cassidy's Rhyhorn mecha fall into the hole. Jessie, James and Meowth then arrive on the scene in their Meowth balloon fitted with extra propellers and recite their motto. The group laugh, and a large plunger is fired out of the bottom of the balloon's basket and attaches itself to Hippowdon. The balloon then starts floating away, with the extra propellers helping it compensate for having such a large weight attached. Ash isn't about to let them steal Hippowdon however, and grabs ahold of the large Pokemon's legs. Dawn and Brock do the same. Cassidy, watching all of this from inside their mecha isn't impressed and tells Butch to deal with the situation. Butch gives her a thumbs up, and pushes a button that fires the Rhyhorn's drill right at Team Rocket's balloon and popping it. The balloon flies off into the distance and the rope holding Hippowdon is cut loose and it and the group all fall to the ground.

The Rhyhorn mecha then bursts from out of the crater it was trapped in and starts moving forward. Ash, Dawn and Brock stand in front of the Hippowdon to attempt to protect it but Butch sends the grabbing claw and smashes into the ground behind them sending them flying forward. Hippowdon then attempts to escape, but the claw grabs hold of its body and pulls it out of the hole it was trying to dig. Just then, a large shadowed figure comes racing onto the scene and smashing into the Rhyhorn. It appears to be a large Slowbro, but is just a mecha designed to look like one. Jessie, James and Meowth are inside, and Jessie starts egging Cassidy on. Cassidy takes the bait and drives their mecha forward and the two machines start clashing against each other. Jessie and Cassidy start arguing again, with both mecha hitting each other over and over again. Ash. Dawn and Brock take this chance to try and escape with Hippowdon who seems to agree and follows them. Jessie fires off the Slowbro shell tail which explodes on contact with the Rhyhorn but has no effect and leaves no damage. Jessie, James and Meowth are shocked, and Cassidy laughs saying that their machine isn't cheaply made like theirs is. She then fires off the Rhyhorn's horn which drills right through Team Rocket's Slowbro causing it to explode and send everyone flying. The force of the impact also releases Parachisu from Hippowdon's mouth much to Dawn's delight. Hippowdon isn't happy about being trapped, caught and blown away and finally gets angry and releases a Hyper Beam at Butch and Cassidy's mech.

The mecha falls apart and the screen protecting Butch and Cassidy shatters. Cassidy is enraged, and decides to settle this with a Pokemon battle. Grabbing a Pokeball from her belt, she calls out her new Pokemon Granbull, and Butch does the same sending out Shuckle. Jessie shouts for Cassidy to stop, sending out Seviper which smashes into Cassidy's Granbull. Jessie then tells James to help her catch the Hippowdon, and James sends out Carnivine which wraps around James' head as James flails about telling it to go do as its told. Seviper and Granbull exchange blows, both Cassidy and Jessie telling their Pokemon to use Bite and both Pokemon reeling in pain from the other's mouth grip. Carnivine and Shuckle then face off, with Carnivine using Bullet Seed on the small Bug Pokemon. Butch tells Shuckle not to take the abuse, and use Sludge Bomb. Shuckle does so, but Carnivine dodges. The attack then smashes into the ground causing an explosion. Ash steps in, telling Pikachu that they can't let Team Rocket get Hippowdon. Pikachu uses Thunderbolt, which zaps both Shuckle and Carnivine sending them flying back to their trainers. Hippopotas then uses Yawn, which sends both Team Rocket groups and their Pokemon to sleep. Hippopotas then uses Sandstorm to whip up all the Rocket members together, before Hippowdon uses Hyper Beam to send them blasting off together. Ash asks if Hippowdon is okay, and the large hippo nods. Dawn then apologies for chasing it around all day and for Parachisu to be trapped inside its body. Hippopotas starts snuggling up to Hippowdon, and Dawn is happy to see it has found a friend.

Elsewhere, Jessie, James and Meowth are moaning about their loss of the day while hanging from a tree. Jessie screams out a warning to Cassidy who has landed head first into the sand somewhere else. Cassidy and Butch pull themselves up from the sand, both incredibly unhappy about being foiled yet again. The episode ends with a very angry Professor Nanba, who after attempting to call Cassidy, has his name said incorrectly sending him into a frenzy.

Thanks to Alfonso for writing this for us