Ash and friends continue their journey across Izabe Island, where they spot a giant stone Poké Ball atop a cliff. They meet a sage named Sigourney, who tells them the story of the giant ball. Once upon a time, a great destructive power was released, but was sealed inside a giant stone Poké Ball by a powerful sage and left in the lake.
Team Rocket overhears this and of course, wants to steal the giant Poké Ball. They show up at the lake and drop bombs on the stone ball, breaking it open. A huge Claydol emerges and headed toward the village, blasting energy that destroys everything in its path. Ash tries to catch it in a regular Poké Ball, but it doesn't work, and neither does attacking it.
They realize they need to lure the Claydol toward the other giant stone Poké Ball. Team Rocket wants to help too, though they have their own wicked motives. Sigourney reads from an old book that Claydol likes eggplants, so Ash and James dress up as eggplants to lure the Claydol to the rock. It turns out Claydol actually hates eggplants, and they escape just in time. Next, they try to use beautiful maidens to lure the Pokémon in (also from the book), with May, Jessie, Meowth, and Wobbuffet dressing up. The Claydol ends up chasing Wobbuffet down a crevasse toward the Poké Ball. The kids push the Poké Ball down the hill, where it gets stuck. A combined attack from Mudkip, Lombre, and Pikachu frees it, and the stone ball finally rolls down to Claydol, capturing the giant Pokémon inside.
Team Rocket then tries to get away in their balloon with the giant Poké Ball, but it's too heavy and they crash elsewhere. The ball rolls away, ending up in the middle of the lake.
While traveling through a canyon, Ash and his friends notice a giant stone Poké Ball on top of a hill. Their curiosities are soon answered by Sigourney, the Izabe Island sage, who recites the ancient tale of the Great Destruction. He informs the group that a powerful Pokémon was sealed in a similar Poké Ball that lies in nearby Izabe Lake. Team Rocket overhears Signourney's story and decides to pursue the contents of the giant Poké Ball.
Sigourney leads Ash's group to the lake, where they see Team Rocket's balloon hovering over the giant Poké Ball. Team Rocket says their motto through megaphones. Meowth pushes a button on a remote and a bunch of bombs explode onto the Poké Ball, opening a giant hole in the top of it. The ball cracks open, parting the waters of the lake and pushing Team Rocket's balloon aside. A giant Claydol appears in the split waters, Sigourney affirming that the Claydol is the menace described in the ancient legend. Meowth pushes another button and hooks come out of the balloon, grabbing the Claydol. The balloon tries to lift the Pokémon up, but it proves too heavy. The Pokémon shoots an Ice Beam at the balloon, freezing it solid before blasting the trio off with Hyper Beam. Moments later, they fall down, landing on Claydol's head.
Claydol starts moving out of the lake and across the land, shooting Hyper Beams to destroy a path in front of it. Ash throws a Poké Ball to try to catch it, but it fails. Sigourney explains that only the giant Poké Ball at the top of the hill can catch Claydol. Brock sends out his Lombre and Mudkip to shoot Claydol with Water Gun, but this only angers the Pokémon and makes it spin rapidly, sending Team Rocket flying into the air. Team Rocket lands near Ash and his friends, and with the evil intention of catching the Claydol, they convince Ash's group that they want to help restore balance. Sigourney flicks through his book again and explains that Claydol likes eggplant, so they decide to lure it with that. Ash and James hold out a basket of them, but Claydol doesn't see it. James and Ash dress up as eggplants, and Claydol sees this and gives chase. Suddenly, Sigourney realizes that Claydol actually hates eggplant, so everyone tells Ash and James to run away. They get out of the costumes just before Claydol stomps on them.
Claydol runs into a rock wall, so it blasts a hole through it. Unfortunately, it is headed for a town, and the people there run for cover. To distract it, Sigourney, Ash's group, and Team Rocket decide to lure Claydol to the mountaintop with a "beautiful maiden" that the legendary text references. Jessie, May, Meowth, and Wobbuffet all dress as maidens, playing musical instruments. They rip off their outfits to reveal different costumes: Jessie is dressed as a ballerina, May as Nurse Joy, Meowth as a cheerleader, and Wobbuffet as a maid. Claydol seems interested and approaches them. While it is displeased with Jessie, May, and Meowth, and blasts them away, it take a particular liking to Wobbuffet and starts chasing him. Wobbuffet continues to play the flute and lead Claydol towards the giant Poké Ball. As everyone attempts to leverage the stone Ball in readiness, Wobbuffet is about to be caught, so Ash sends Swellow to rescue it. However, Swellow only gets Wobbuffet's wig, and Claydol quickly realizes that Wobbuffet was only in disguise and gets angry. Fortunately, the ball rolls down the hill, but it gets stuck. Brock sends out Mudkip and Lombre to use Water Gun to weaken the obstruction, and Pikachu breaks the rock with a Thunder. The ball hits Claydol, and successfully seals it inside.
Suddenly, everyone notices that Team Rocket are missing, and quickly realize that the trio are trying to steal the giant Poké Ball. They grab their catch with a giant claw. However, the ball ends up rolling down a hill, dragging the balloon down with it. The balloon breaks free, sending Team Rocket flying away. The ball continues hurtling before finally settling in Lake Izabe, just like the original Poké Ball was. Ash and Brock wonder whether the giant Claydol was even a real Pokémon given its immense power. Even so, Sigourney and the others hope that Claydol will rest well and one day be able to live in peace.