A Wailord blockage has trapped the boats in Canalave's harbor, and that means Dawn can't take a ferry to her next Contest. There's nothing to do but sit down for lunch, but a wild Luxio and its Pokémon accomplices steal the food! Pikachu and Piplup give chase, but run straight into Team Rocket. As always, Team Rocket tries to grab Pikachu, but Ash catches up with them and escapes into the sewer with his buddy. Piplup uses Whirlpool to toss Team Rocket, and now it's up to Ash to find his way back to his friends. As he wanders the sewers, he comes across the Luxio and its pals. They stole the food to feed a stranded Wailmer that somehow ended up in the sewer!

This Wailmer belongs to the Wailord group out in the harbor, and Ash offers to help Luxio get it back to its friends. He discovers there are many species of Pokémon living in the sewer, and Luxio is their leader; with all of their help, he can get Wailmer up a tall waterfall inside the sewer. Ash's idea is to make a giant ice ramp and push Wailmer up on a sled! Thanks to a last-minute assist from a Venonat, the plan works like a charm. As Wailmer swims even closer to freedom, Dawn and Brock find their way into the sewer and reunite with Ash. Things are looking up!

But one problem remains: a touchy Swampert mistakes Wailmer and the others for intruders in its territory, so it attacks. Ash's Grotle knocks it out and Wailmer swims out into the harbor... then evolves into a Wailord, too big to fit under the drawbridge up ahead! To force the drawbridge open, Pikachu, Luxio, and Pachirisu charge up the drawbridge controls, and Wailord swims through in time to avoid a second attack from Swampert. The new Wailord rejoins its pod and happily swims away as Ash thanks Luxio, then goes to eat his long-delayed lunch—he's earned it!