Ash is looking forward to battle in the next Gym, which is the Azalea Gym in Azalea Town. As Misty spots large houses and comments how beautiful the place is, Brock gets excited because whenever there is a beautiful place, he can find many beautiful girls. Misty asks why he thinks that and Brock points out to a girl standing on the edge of a cliff. As soon as Marill appears, Misty, who just loves water Pokémon, attempts to capture it. But the Poké Ball simply hits Marill on the head, causing it to cry out loud. Brock quickly comforts the Marill. Ash points out that Marill must already have a Trainer because of the pink bow tied on its tail. Misty tries to hold it, but Marill doesn't seem to like Misty and cries again.
Jessie, James and Meowth make their appearance, disguised as farmers, and they offer the group a lift. Unaware of the plot, they hop on the vehicle. Just then, two hands grab hold of Pikachu and Marill and make their escape after getting rid of Ash, Misty, and Brock. Marill lets out an ear-splitting cry, making Meowth lose his control over his driving. The truck eventually crashes into a railing and Team Rocket blasts off into the air once again. Pikachu and Marill ends up rolling down the hill towards the riverside. Ash tries to go after them and ends up landing into a tree. On the other hand, Misty continues down the hill and successfully grabs the two Pokémon. Unfortunately, she couldn't stop and falls into the river.
The girl they were gazing at before meets up with Ash and Brock, and asks them about her Marill. Brock, who goes gaga for beautiful girls, introduces himself to her and learns that her name is Wilhelmina.
Misty, Pikachu and Marill survive the river, but Marill begins to cry again. With her temper getting the best of her, Misty yells at Marill, making it more upset. Marill then runs off, leaving her pink ribbon behind. Misty tries to hold Marill, but the blue mouse simply refuses to be with her. After calming down a bit, Misty suggests to find Marill's Trainer by using its sensitive ears. During the search, Misty gets impatient with Marill and the Water-type cried.
Ash has full confidence that Misty will take care of Marill. But Wilhelmina is still worried about her Pokémon and blames herself for its disappearance. Brock starts comforting her. Afterward, Togepi spots Marill's pink ribbon. Meanwhile, the other group gets in trouble with a bunch of Beedrill. Ash, Brock, and Wilhelmina hears Pikachu screaming and runs towards the sound. However, they miss Misty, Pikachu, and Marill.
The situation becomes more critical as Misty, Pikachu, and Marill reach a dead-end. Thinking quickly, Misty tells Pikachu to use ThunderShock. The ThunderShock manages to scare off the swarm of Beedrill. Just when things seem okay for them, rain begins to fall. Misty and the two Pokémon find shelter under some trees. As the lightning starts scaring Marill, Misty tries to console it. And when the lightning is about to hit Marill, Misty goes out of her way to save it.
Team Rocket make their appearance again after the rain stopped and grabs the two Pokémon. Misty manages to grab hold of Marill, but ends up falling. However, Ash's Chikorita saves them in the nick of time. Jessie and James battle against Ash and Misty with Arbok and Weezing. Arbok's Poison Sting attack almost hit Misty, but Marill uses Water Gun to save her. After that, Pikachu blows Team Rocket away with Thunderbolt.
During the ending, Misty is nearly in tears as she waves goodbye to Marill.