Ash, Misty, and Brock travel to the water city of AltoMare where Ash and Misty compete in the Water Chariot Race which Misty ends up winning. After the race Ash ends up saving a girl from Annie and Oakley, two members of Team Rocket who are in the city to try and capture the Legendary Pokémon, Latios and Latias, for Giovanni. Little does Ash know, but this girl is actually Latias in disguise. Ash follows her back to her secret hideout where he meets her brother Latios. Ash also learns that Latias takes the form of her best friend Bianca. Bianca and her grandfather tell Ash all about Latios and Latias and Ash plays with them. That night, Annie and Oakley invade the hideout and capture Latios and steal the Soul Dew in order to power the D.M.A. Now Latias must find Ash and the others and help to save AltoMare and her brother!

Pikachu and some of the other pokemon camp out in the woods and help the Pichu brothers get on the train.

On their way to the Whirl Cup competition, Ash and friends are fortunate enough to pass a small mountain village just as an annual Chinchou migration is about to occur. Long ago seismological forces had combined to lift the mountain out of the depths of the sea, bringing along with it the undersea nesting ground of these Chinchou.