After winning Lt. Surge's Thunder Badge, Ash, Misty, and Brock make their way towards the harbor. They wish they could all go on a cruise, but Brock points out that the tickets would be far too expensive for them. Suddenly, two schoolgirls show up, offering free tickets to a Pokémon party on the St. Anne. Ash and his friends are ecstatic, and rush to find the ship.
Little did they know that those two "schoolgirls" were actually Jessie and James in disguise. They rush up a tower nearby, and call their Boss. Meowth is broken hearted when he sees that the Boss has a Persian, as he thought he was the Boss's favorite. The Boss explains his disappointment with all three of them. He wants perfection from all his workers. He says that if they want to make him happy, they can make sure that the plan they are working on doesn't fail. He asks if all the tickets for the St. Anne were handed out, and Jessie replies that the Pokémon trainers were all happy to take them. He says that his men have secretly boarded the ship, and, when the time is right, they will steal all the passengers' Pokémon. He repeats that failure is not an option, and signs out.
Ash and his friends board the St. Anne and enter a huge room. Inside are several hundred fellow Pokémon trainers and merchandise booths. The trainers are all showing off their Pokémon and Ash is about to show off his Charmander and Squirtle when he notices a battle going on between a tall gentleman and a young trainer. The gentleman sends out a Raticate, and the defender sends out a Starmie. The Raticate quickly wins with a Super Fang attack that cracks the Starmie's gem. The boy is worried, but the gentleman says that he was lucky. After giving the boy some advice, he asks for another challenger. Ash is only to happy to oblige, and sends out Butterfree.
Team Rocket comes out of the kitchen dressed as waitpersons, and marvel at how many trainers there truly are on the ship. They can't wait to steal the Pokémon, and James daydreams about having them all. Jessie brings him back down to earth by reminding him that the Pokémon are going to the Boss.
Ash and the gentleman start their battle. It's a good match, and Ash is about to win, when the gentleman picks up his Raticate and calls the match a draw. Ash is disappointed.
A bit later, James is walking around when a booth vendor attracts his attention. The vendor tells him that a Magikarp lays 1000 eggs at a time, and each of the Magikarps that hatch from those lay 1000 eggs. Soon he'll have a more than a million Magikarp, and at about $100 a pop, that adds up to a lot of money. James agrees to buy one as well as a few instructional sets for $300.
Meanwhile, Ash and his friends are busy stuffing their faces. The gentleman shows up again, with a young woman. He tells Ash that he was very impressed with Ash's Butterfree. The young woman agrees, but Brock doesn't hear. He is stunned with her beauty. Misty tries to snap him out of it, but he's gone. Ash thanks the man and adds that Raticate wasn't to bad itself. Then the man proposes a trade, telling about how friends trade Pokémon so that they become better friends and so on. Ash asks Brock if he should go through with it, but Brock's mind is elsewhere. Ash agrees, and they trade using a strange looking machine. Raticate is now Ash's, but he doesn't seem to sure about it all.
Team Rocket is having their own problems. Jessie and Meowth are furious at how well James was fooled. James defends himself, saying that, not only is Magikarp a gold mine, but it came in a solid gold Pokéball. Meowth yells that it is only gold-plated, and scratches at it, revealing the true colors underneath. When Jessie asks how he got the money for it, he meekly replies that he used both of their advanced salaries. Jessie is enraged, and tells him to get their money back.
As the boat sails on, Ash still thinks about the trade he made to someone he didn't even know. He wonders if the gentleman will take care of his Butterfree the way he did. He thinks about trading back. At that moment, several Team Rocket members appear in full uniform. It's time to attack, but James is still looking for the person who sold him the Magikarp. Jessie tells him to forget about it for the moment and do the job. They do their motto, and start sucking up everyone's Pokéballs. Ash tells everyone to fight back, and they are able to beat Team Rocket off.
The St. Anne gets caught in a storm and starts to pitch. Ash decides to take get his Butterfree back from the gentleman, and he reluctantly consents. When the ship starts to take on water, the passengers start to evacuate. Ash and the gentleman quickly trade, but a large wave hits the ship, causing Ash to drop Butterfree's Pokéball. He runs after it, with his friends following quickly behind. Team Rocket is experiencing the same problem, as has James dropped Magikarp as well, and since neither Jessie or James want their money to roll away, so they chase after it. Both Team Rocket and Ash get their Pokémon, but another wave hits the ship and they are all knocked unconscious. The ship flips over and sinks to the bottom of the ocean with Ash, Misty, Brock, and Team Rocket still trapped inside...