Ash, Misty, and Tracey are once again riding Lapras among the Orange Islands. Ash is polishing the G/S Ball when he notices water being kicked up over the horizon. They think it's a motorboat, but when it roars past, they realize that it's a kayak being rowed by a dark-skinned Nurse Joy. They decide to follow it and see where she was going in such a hurry.
Seconds later, Lapras reaches a remote island that the kayak is beached on. Tracey starts to track some footprints in the sand, and, after Ash retreats Lapras, he and Misty follow. Soon enough, Tracey loses the trail on some rocks. They look around for a few moments, and Tracey comments that this Nurse Joy looked a lot more muscular than the average Nurse Joy. As he gives Ash and Misty some estimated measurements, a giant Magikarp flies out of the water next to them and lands on the rocks. It flops around for a while, and Ash says that they should help it back into the water. This is a lot easier said than done, because of the Pokémon's size.
Nurse Joy shows up behind them, telling them that all it needs is some calcium. She walks right up to Magikarp and it instantly calms down. She feeds it some tablets that Chansey hands to her then picks it up over her head, tossing it back into the water. Nurse Joy tells Ash and his friends that she and Chansey travel to islands that are too small to have Pokémon Centers of their own. All three introduce themselves, and Ash's stomach growls. Joy invites them to the clinic on the island for lunch.
As they eat, Ash and his friends decide to try to help Nurse Joy with what she does. They go outside to find her attending to Ash's Lapras. She tells him that it's fine, but it needs a little rest from the speedy journey they had done. They ask to help and she agrees. Moments later, they're all in kayaks. Nurse Joy speeds off, with Ash and his friends slowly following. They do catch up, and help her out with several things, from treating a Mankey who refuses to come down a tree to giving a giant Onix a shot.
On one of the journeys between islands, Ash and his friends are once again lagging behind. They come upon Nurse Joy's kayak, empty, and get worried. Tracey worries that a Gyarados turned them over, and they notice a pink object surface. They paddle over, thinking that it's Chansey, but it turns out to be Jigglypuff (oh no!!). They quickly paddle away in fright.
After a few moments, they stop for a rest. Suddenly, Chansey and Nurse Joy surface next to them. She tells them that she went down to treat a Cloyster and that the current must've drifted them away from the kayak. Chansey goes to get it, and she offers to show Ash and Tracey how she goes about treating Pokémon that are underwater. They swim down to the ocean floor and watch as Joy treats a Shellder. Tracey raves to himself about how dedicated Joy is, and Ash runs out of air. Before he can surface, a Dewgong grabs him. Fortunately for him, Joy gets it to let him go, and they go back to the surface.
She takes them to a clinic on another island, and apologizes to Ash for what Dewgong did, saying that it was only trying to play. Tracey asks her if it would be easier to work at a Pokémon Center like all other Joys, and she tells them a story. When she was a young girl, she found a baby Magikarp on the shore. She took it home and treated it. When it was better she set it free. Months later, she and her family (all Nurse Joys.) were on a boat ride when she fell into the water. The same Magikarp that she had treated saved her. She tells Ash and his friends that it was that day that she decided to spend her life caring for Pokémon. The Magikarp from earlier is the same one. They go back outside, and the wind is starting to blow. Joy tells Ash and his friends that she has to treat some baby Seel. She leaves, despite Tracey's warnings of a hurricane. He decides to follow her, and Ash decides to follow him (much to Misty's chagrin).
The rain pelts down, and the sea is getting really rough. Ash and his friends approach Joy, but a wave turns them all over. She tells them to send out a water Pokémon and follow her to a nearby island. They manage to safely get to it, and the storm passes without much trouble. Ash and his friends apologize for wrecking Joy's schedule, but she dismisses it, telling them to take a rest. After which, she says, they'll go check out the baby Seel.
Meanwhile, Team Rocket watch from the Magikarp sub (wow! I was starting to think that we wouldn't be seeing them this episode!). They plan to steal both Pikachu and Chansey, and Meowth uses their secret weapon (wait, did he call James, "Jimmy"?). He hits a button on a remote control, and a missile fires out of the water directly towards Nurse Joy and the rest. It explodes, and a net falls around them. Team Rocket surfaces, says their motto, and tease Ash and his friends. Nurse Joy thinks about the sick Seel that are counting on her, and tries to break the strands of the net. It's no use.
Suddenly, something slams into the Magikarp sub. The giant Magikarp jumps out of the water, and starts hitting Team Rocket's sub. It's no use, however, as the metal is too strong for it. Nurse Joy starts to cry for both Magikarp and Seel, and Magikarp starts to glow. It evolves into the biggest Gyarados this side of Vermillion! With one swipe of it's tail, Team Rocket and their sub is cast out of the episode.
Gyarados turns to Ash and his friends, and they get worried. It lunges, and Ash yells out in fright. It stops though, and Joy pets it. It takes the net off of them, and she thanks it.
Nurse Joy hurries to the Seel, with Ash and his friends close behind. Everything goes fine, and they thank her as well. As Nurse Joy pets Gyarados, Ash and his friends prepare to leave. Joy turns to Ash and tells him that there is an Orange League Gym on Naval Island, which isn't far away. They set off on Lapras towards their next challenge.