Ash and his friends are taking the Cyling Road toward Hearthome City, but when the weather turns bad and Brock's Pokémon Egg is about to hatch, they quickly take refuge at the nearest Pokémon Center. However, the Nurse Joy at the Center has a serious case of the blues. Thanks to the Cycling Road, everyone pedals right past her Pokémon Center and she's convinced it's her fault that the place is so empty! With a little encouragement from our heroes, Nurse Joy gets back some confidence in time to help hatch Brock's Pokémon Egg, which turns out to be a Happiny.

Everyone has fun taking care of Happiny, until Team Rocket shows up, snatches it, and makes a getaway in their Meowth balloon. Jessie wants Happiny to evolve into Chansey and become a nurse! Brock and his friends have to chase down Team Rocket while also trying to keep Nurse Joy's spirits up, but Team Rocket has an even more difficult task ahead: cheering Happiny up! Happiny likes to carry a smooth stone in its pouch, and it's not impressed by any of the rocks that Team Rocket has to offer.

Now Team Rocket has another problem to deal with, because Brock and the gang have finally caught up with them. Nurse Joy is feeling confident enough to help our heroes battle, too! But it comes as a surprise to everyone when pint-sized Happiny turns out to be so strong, it can clobber Team Rocket on its own. Pikachu helps finish the battle, and then our heroes are ready to get back on the road to Hearthome City... and Nurse Joy is ready to get back to work!