When Dawn and Ash reach Sandalstraw Town, they meet two familiar friends: Kenny and Barry! Kenny plans to enter the Sandalstraw Contest, while Barry is training for the upcoming Pokémon Ping-Pong competition—but their conversation is cut short when Piplup glows as if it's ready to evolve! However, Piplup isn't well, so it's off the Pokémon Center so Piplup can rest. Dawn uses this opportunity to talk to Piplup about Evolution, but it gets upset and runs away!

Everyone splits up to search the nearby forest, and Dawn finds Piplup using Bide to stop its Evolution. She doesn't understand why it won't evolve, and that makes Piplup angry enough to run from her again. When Dawn chases Piplup deeper into the forest, she finds it stuck in an Ariados web. Dawn saves Piplup from the Ariados, but then they're surrounded by an entire swarm of Ariados! Piplup uses Bide to defeat them, and Dawn realizes this is just like the day when she and Piplup first met.

Barry and Kenny are also searching the forest for Piplup, but Barry's Empoleon and Kenny's Prinplup are kidnapped by Team Rocket's giant Piprinoleon robot! The robot finds and grabs Piplup too, so Dawn sneaks inside the robot and confronts Team Rocket. Piplup forces its way through a duct in the robot to reach Dawn and back her up; all this time, it's wanted to remain a Piplup so it can protect Dawn. Piplup uses Whirlpool to bust open the robot, and Dawn's friends arrive to provide support. With their help, Piplup sends Team Rocket shooting into the sky, and Dawn promises to always be partners with her Piplup. No Evolution needed!

Later, at the Pokémon Center, Nurse Joy gives Dawn an Everstone to prevent Piplup from evolving. Now everyone can concentrate on the Sandalstraw Contest—as well as practicing their Pokémon Ping-Pong!