Ash, MIsty, and Brock arrive in Mossgreen Village, a village that's so small it doesn't have a Pokémon Gym. Since, there's no gym here, Ash doesn't want to stay but Brock points out that their bag of potions is empty and they need more. Meanwhile, Team Rocket is following them, waiting for the perfect time to catch Pikachu. But Meowth is lagging behind and he is very sick. Jessie and James think that losing Meowth is worth it to catch Pikachu. They are yelled at by a girl who thinks they are abandoning Meowth. The girl nurses Meowth back to health and Meowth falls in love with the girl.
Ash and his friends have arrived at a medicane shop to but some potions. When they enter, they are greeted by an old woman who is grinding herbs. When they say they want to but some potions, she offers them a snake root that will cure insomia and grow hair on their nose and tongue. The old woman's granddaughter enters the shop, who is also the same girl that healed Meowth. The girl's name is Cassandra and Brock falls in love with her. Brock tells her that he wants be the world's greatest breeder and Cassandra says that she wishes she could battle someone. Ash tells her that he will battle her. Cassandra starts the battle by sending out Paras and Ash sends out Pikachu. Pikachu tries to be nice to Paras, but Paras is terrified. Team Rocket is spying on the battle and making plans to catch Pikachu, but Meowth is focusing on Cassandra and trying to think of a way to repay her for healing him.
Cassandra tells Ash that she wants to battle so Paras can evolve and she can use Parasect's giant mushroom to make a super healing potion, but Paras is too afraid to battle. Ash agrees to lose the battle so Paras can gain some experience. Pikachu starts the battle and fires a small electric bolt at Paras, but it easily knocks it out. Misty suggests Ash try using a different Pokémon, so he switchs out Pikachu with Squirtle. But just a few drops of water knocks Paras out again. Ash goes for broke and sends out Charmeleon. He tells Charmeleon to go easy on Paras, but it knocks out Paras and sends it flying with Flamethrower and Tail Whip. Paras runs away crying. Ash tries to recall Charmeleon, but Charmeleon attacks Ash, apologizing him. Pikachu has to knock out Charmeleon before Ash can recall it. Ash is shocked that Charmeleon is disobeying him and Misty tells him to worry about this later and that they need to find Paras.
When Paras runs away, it finds Team Rocket. Meowth, who wants to help Cassandra, convices Jessie and James to help Paras get stronger because losing is something Arbok and Weezing are good at. Arbok lets Paras knock it out and Weezing does the same. Jessie and James cheer Paras on.
Ash and his friends find Paras soon in a tree, with Team Rocket hiding nearby. Because Paras looks so confident, they think its ready to battle again. Pikachu lets Paras knock him out and Ash sends out Charmeleon and it disobeys Ash again. Ash doesn't understand why Charmeleon was't commad to him and Cassandra's grandmother explains that if a Pokémon's strength exceeds the trainer's skill level, it won't obey the trainer because his side-effect problem.
Ash tries to recall Charmeleon, but it uses Flamethrower on Ash before turning its attention to Paras. Team Rocket jumps out of the bushes to protect Paras, but Charmeleon sends them blasting off again. Paras defends itself by putting its claw in front of it and its claw hits Charmeleon in the stomach and knocks it out. Ash recalls Charmeleon and everyone cheers for Paras just as Paras evolves.
Ash and his friends say good bye to Cassandra and her grandmother, who reminds Ash to learn to control Charmeleon. Team Rocket comes by and they ask if Meowth can be the mascot for the company Cassandra is starting for her super potion. Cassandra's Grandmother says she has found a Persian to be the mascot and doesn't need Meowth. Team Rocket walks away sadly as Cassandra promises that she will treat Persian like Meowth.
- The "Who's that Pokémon?" in this episode is Paras.