The episode begins with Dawn’s Piplup sitting underneath a waterfall. Suddenly, Piplup begins to glow as if it was going to evolve. With much concentration and focus, Piplup stops glowing and stops evolving. It then shows Piplup panting in exhaustion.
In the next scene, Ash, Dawn, and Brock are standing outside a Pokémon Center. Dawn releases all of her Pokémon and begins to encourage them for the next Pokémon Contest and her fifth ribbon. During her Pokémon’s cheers, Dawn’s Piplup starts teetering and falls over. Upon being asked if it is okay, Piplup acts strangely and spins around in circles. Out of nowhere, Barry runs out from behind the Pokémon Center and runs into Ash, threatening to fine him for obstructing his path. Moments later, Kenny walks out from behind the Pokémon Center as well, greeting Dawn as DeeDee. Barry is surprised that Dawn and Kenny already know each other, and declare that they are both from Twinleaf Town. Barry claims that Kenny is going to win the next Pokémon Contest, and Barry is going to enter and win the Pokémon Ping Pong competition with his Empoleon. As Barry and Empoleon show off their moves, Piplup begins to glow again, showing signs of evolution. However, Piplup starts concentrating again and using Bide to stop the evolution process, then collapses. The team quickly takes Piplup to Nurse Joy.
In the Pokémon Center, Piplup’s vital signs are monitored and Nurse Joy states that Piplup merely used an excessive amount of energy. Dawn is relieved after Nurse Joy assures her that everything is going to be fine.
The show then switches to a scene of the team eating at a restaurant with Barry and Kenny. They discuss how after the evolution of Piplup, it will gain a massive amount of power, but as a result, Dawn must modify her training and usage styles. Dawn says she is prepared for Piplup’s evolution, as she already experienced Swinub evolving into Mamoswine. Beside Dawn, Brock appears to be in deep thought, but after Ash asks if there was anything wrong, Brock says that everything is fine. Right outside the restaurant, Team Rocket is observing the team through the window and elaborates on their plans to steal Piplup.
Back in the Pokémon Center, Piplup awakes from its bed and looks at its reflection in the window. While imagining what it would look like as a Prinplup, Dawn walks in the room with some food. Piplup refuses the food, and Dawn places it on the table beside the bed. Dawn then chats with Piplup about how awesome it will be when Piplup evolves into Prinplup. Suddenly, Piplup spins around to face Dawn and shows signs of distress and unhappiness. When Dawn assures Piplup that there’s nothing to be afraid of, Piplup starts glowing again. It immediately uses Bide again to stop the evolution process. When Dawn confronts Piplup as to why it continues to use Bide to stop its evolution, Piplup breaks out of Dawn’s grasp and runs out of the Pokémon Center through the window. Dawn quickly exits the bedroom and runs into the rest of the team and asks for help.
Outside the Pokémon Center, Brock explains that it is likely that Piplup does not want to evolve. After splitting up and running into the forest to find Dawn’s Piplup, Dawn sees a glowing light within the depths of the trees. The scene then switches back to the waterfall from the beginning of the episode, and shows Piplup using bide again to stop the evolution process. From exhaustion, Piplup falls off its perching rock and into the water. Dawn quickly picks up Piplup and asks why it is trying to avoid evolving. Piplup then shows signs of anger, uses Bubble on Dawn, and runs off into the shrubs. When Dawn enters deeper into the forest, she finds Piplup stuck in a web. Upon running toward Piplup to rescue it, Dawn gets attacked by an Ariados. With Piplup using Bubble on Ariados, Dawn manages to get Piplup free and catches it when it falls. While Dawn checks to see if Piplup is safe, an entire swarm of Ariados appear and charge up to use Hyper Beam. Piplup pushes Dawn aside and stands in the path of the Hyper Beam, using Bide to absorb the shocks. Then, it releases energy, blasting the Ariados into the distance. It then falls over in exhaustion again.
Somewhere else in the forest, Barry and Kenny are seen searching for Piplup with no success. Suddenly, two mechanical hands come out of nowhere and grab Kenny’s Prinplup and Barry’s Empoleon. The hands spin both Pokémon at high speeds to prevent them from using Bubblebeam and Hydro Cannon. When Barry demands the culprit to reveal itself, a giant machine emerges from the distance.
Back with Dawn and Piplup, Dawn recounts a memory of the first day she me Piplup, when a similar incident occurred. Piplup had saved Dawn from a different swarm of Ariados, and that was the reason Dawn selected Piplup at Professor Rowan’s laboratory that day as her first Pokémon. Ash and Brock appear from the forest path to meet Dawn, and are relieved that both Dawn and Piplup are okay. Suddenly, the same mechanical hand that captured Prinplup and Empoleon comes out to grab Piplup. The entire culprit emerges and comes to focus, and becomes clear that it is a Prinplup Robot made by Team Rocket. Barry and Kenny come into the scene, demanding that they get their Pokémon back. Piplup is thrown into the machine with the other two captured Pokémon. After some talking by Team Rocket, Ash commands Pikachu to strike the machine with Thunderbolt. The machine puts its arm out and absorbs the shock, rerouting the electricity into the machine and back out to the room in which Prinplup and Empoleon are contained. As Team Rocket slides away in their machine, Dawn jumps on and tries to save Piplup.
Inside the machine, Team Rocket are discussing their victory. Suddenly, Dawn enters through a passageway in the top of the machine and demands that Piplup be returned. In the room where the stolen Pokémon are contained, Piplup pecks its way out of the room using a loose vent covering. Joining Dawn’s confrontation of Team Rocket, Piplup declares that if Team Rocket wants Dawn, they’ll have to go through it first. Piplup claims that it will protect Dawn just like it has always protected her since the first day. Piplup uses Whirlpool on Team Rocket and their machine’s head explodes. Prinplup and Empoleon are released in the explosion, and Team Rocket prepares for a battle with Dawn. Piplup easily rids Carnivine and Seviper with Bubblebeam. Suddenly, Piplup starts glowing again and shows signs of evolution. Team Rocket tells their Pokémon to resume attack, but suddenly get shocked by a bolt of electricity out of nowhere. Ash and the team emerge from the distance, and Kenny and Barry embrace with their rescued Pokémon. Team Rocket’s Pokémon are then finished off with Pikachu’s Thunderbolt followed by Piplup’s Whirlpool. After Team Rocket blasts off, Dawn explains to Piplup that she now understands why it doesn’t want to evolve, and says that they will always be a team.
Back in the Pokémon Center, Nurse Joy presents the team with Piplup, Prinplup, and Empoleon, declaring that all of them are in good condition now. She also gives Dawn a gift. Chansey hands over an Everstone, a stone that will prevent Piplup from evolving so it doesn’t have to use Bide each time. Just outside the Pokémon Center, the team begins to train again for the upcoming contests and competitions.