The episode starts with Ash and company camped out near a lake. Ash was cleaning his Poké Balls in preparation for his rematch with Brawly. May comments that Ash was really working hard. Max then commented that she should follow Ash's example. After Ash finished speaking to his Pokémon, Corphish wandered away after it spotted a piece of seaweed. It began to eat the long piece of seaweed which was tangled up with some buoys attached to a rope. It ate the buoys as well. Ash told it to stop saying that it was going to get sick. Corphish pulled on the rope causing it to snap. Its claw went flying backwards and smacked Ash. Later, Ash introduced Corphish to all of the Pokémon. Corphish greeted them back by smacking them. May grabbed her Pokémon and began yelling at it, saying that it would never make friends that way. Brock disagreed, saying that it might be how Corphish say hello.
Later during breakfast, May notices that her Wurmple was not eating and asked if it was sick. Torchic offered its own food to it but it still refused. Corphish then appeared out of nowhere and began eating both Wurmple and Torchic's food. All of a sudden, a robotic hand comes from above and grabs Pikachu. Team Rocket then start their motto wearing Corphish claws. They put Pikachu inside an electric-proof cage, rendering its electric attacks useless. May then told her Wurmple to use String Shot on Team Rocket's balloon. All four Trainers grabbed on to the string of silk trying to hold Team Rocket back. Ash then made the mistake of telling Corphish to help. When it grabbed the string, it snapped it causing Team Rockets balloon to go flying out of control and crash. May started to yell at Corphish but Max said that it was Ash's fault for telling it to help. They then pursued Team Rocket.
It didn't take them long to find them. Ash commanded Corphish to attack with BubbleBeam which caused Pikachu's cage to go flying. James attempted to stop them with Cacnea but it turned around and hugged him. Jessie then called out Seviper who caught Pikachu's cage with its tail. May then told Wurmple to use String Shot to grab Pikachu's cage. It worked and Pikachu was back in Ash's arms. May thanked Wurmple saying that it was the best. Jessie felt the need to show off her Wurmple as she thought hers was better. Brock then said that all Wurmple looked the same to him. May and Jessie began to argue with each other over whose Wurmple was cuter. Then Jessie's Wurmple started to glow. A few seconds later, May's Wurmple also started to glow. Both Wurmple then evolve into Silcoon, or so Jessie thought. When Jessie picked it up, James and Meowth noticed it looked different from May's Silcoon. But they ignored it. They attacked Ash again but he countered with Corphish's Crabhammer which sent Cacnea flying backwards. Ash then told Pikachu to use Thunderbolt which sent Team Rocket blasting off.
As they began to celebrate their victory, Corphish's skin turned bright red and it falls over. Brock checked its temperature and discovered it had a fever. Ash reached for its Poké Ball but then realized he left them back at camp. Convinced there was no time to go back, Ash decided to carry Corphish to the Pokémon Center. He took Pikachu with him while leaving Treecko and Taillow behind. As Ash began his hike up the mountain, he noticed Corphish becoming hotter. He stopped to think how he could bring its fever down and spotted water trickling down the mountain side. He scooped some of it up with two big leaves and gave it to Corphish which helped a little. Ash then heard the sound of his stomach grumbling realizing he never got to eat breakfast because of Team Rocket. Pikachu then spotted a Pecha Berry tree. Ash picked some Berries off of it. As he was about to eat one, he realizes he stepped on a Shroomish. He apologized to it but the Shroomish did not accept it. It attacked with Stun Spore and Ash ran away with his Pokémon as fast as he could.
Later, Ash began to see Dewford Town in the distance. All he had to do was cross a river. As he began to cross a school of Carvanha began to attack and scared him out of the water. As he began to think how he could cross the river, he spotted a rowboat near the shore. The Carvanha started to attack again and Ash told Pikachu to hold them off with Thunderbolt. It worked for a little bit but they came back and ate the boat. Ash ran back to shore and had to think of another way to get across the river and quick. Corphish's fever was steadily increasing. A little bit down stream, Ash spotted a bridge. Thinking their worries over, Ash was disappointed to see that the bridge had been destroyed. He decided to just cross the river by wading through it. Ash put Pikachu and Corphish on a wooden plant and carried them over his head. The Carvanha soon spotted him and began attacking. Ash started to move quicker as the shore was just feet away. He told Pikachu to jump to shore and to attack Carvanha with Thunderbolt. Pikachu does its best to keep them at bay but a couple of them managed to attack Ash. Corphish started to worry about Ash. Ash promised Corphish that he wouldn't let anything happen to it. One Carvanha attacks Pikachu making it unable to stop any futher attacks. As a group of Carvanha were about to pounce on Ash, Corphish fired a BubbleBeam attack at them. It stopped them long enough for Ash to get to shore. Relived, Ash takes a small break and thanks his Pokémon before going to the Pokémon Center. Around sunset, Nurse Joy told Ash that Corphish would be just find in the morning. It seemed that the buoys that Corphish ate earlier is what made it sick. Nurse Joy asked why Corphish ate it and Ash couldn't come up with an answer.
Later on Brock, May, and Max are seen around a campfire. All of a sudden they started to hear what Brock believed to be an Aron. Max found this strange as Aron usually stayed in caves and never came out on the beach. They soon came across a tape recorder with Aron's voice on it. Before they could wonder why it was there, they were all trapped by cages. Everyone except Taillow that is. They soon found out that it was Team Rocket who set the trap. They then discovered that Pikachu wasn't with them. James realized that only two of the traps were activated and accidentally activates the third, which trapped Team Rocket as well. Treecko attempted to break the cage with Slam but to no avail. Little did they notice, the tide started to come in. Back at the Pokémon Center, Ash was at Corphish's bedside dreaming of being in a battle with it. He commands it to use Crabhammer and Corphish lightly bonks him on the head. Back at the beach, Brock finally realized that the tide was coming in and that they were all at risk of drowning. Brock then looked at Taillow and got an idea.
The next morning, Corphish felt a hundred percent better and Ash noticed it. Then Taillow came flying in from the window with a tape recorder around its neck. Ash played it hearing Brock's voice on it. He told him the situation and told him to hurry. Back at the beach, the tide was already up to their necks. They then spot Corphish swimming at full speed towards them. Following it was Ash and Nurse Joy in a speed boat. Ash then told Corphish to use Crabhammer on the cages which immediately sets everyone free. Back at the dock, Team Rocket thanked Ash for saving there lives. However this did not stop them from making one last attempt to steal Pikachu. Ash told Pikachu to use Thunder on them followed by Corphish's BubbleBeam which blasted them off for the second time. Afterwards Brock began to thank and flirt with Nurse Joy at the same time. May and Max then thank Corphish. Corphish happily started to smack everyone around.
