As Ash and Iris continue toward Striaton City, they once again run into Oshawott, who officially joins Ash's Pokémon team! Along the road, they stumble into a deep hole, and are rescued by a boy named Dan. He takes them to his family's resort hotel, where they discover that the hotel's famous hot sand spa has been destroyed by several similar holes.

Dan explains that a group of friendly Sandile often come to the resort to bask in the hot sand, but they've recently started behaving oddly, digging these huge holes and turning hostile toward the guests. To top it off, the leader of the Sandile suddenly appears, grabs Pikachu and Oshawott in its jaws, and runs away with them!

When Ash and friends chase after the Sandile, they discover several geysers beginning to erupt all around the area, trapping many wild Pokémon on a small island in the midst of boiling water. Ash, Iris, and Dan figure out that the Sandile have been trying to save these Pokémon and the hotel's guests by scaring them away from the geysers. When the Sandile form a bridge by locking tails, Ash crosses over to help the frightened wild Pokémon to safety. Iris also pitches in by getting Ash back to solid ground in the nick of time!

Back at the resort, the geysers have flooded the sand bath, turning it into a hot spring. Our heroes can't help but enjoy a little rest and relaxation before resuming their journey through the Unova region!

Pokemon.com Synopsis