Ash, Misty, and Brock arrive in Gringey City where everything is dark, highly polluted, and gloomy. Pikachu isn’t feeling well, its face is red and sparks are coming out of its cheeks. Ash rushes Pikachu to the Pokémon Center while a shadowy Pokémon watches him.
Meanwhile, in the sewer Jessie and James are planning to dive through the sewer system to get into the center to steal Pokémon. They complain about how awful it smells. Meowth gives scuba suits to wear and tells them that he will stay and pump air into their suits. Jessie and James are reluctant to dive into the filthy sewers. Meowth pushes a button that gives them an electric shock and he forces them to dive.
At the Pokémon Center, Ash rings a bell on the front desk and Nurse Joy comes out. Its late at night and she is very tired. She says Pikachu has a cold. Ash yells at her for not being helpful and Nurse Joy explains that the sparks coming from Pikachu is an early sign of a cold in electric mouse Pokémon. She suggests that Ash and his friends leave Pikachu there for the night and come back for it in the morning, that Pikachu will also be better in the morning.
At the same time, a group of Grimer block the water flow into the hydroelectric power plant, causing the power to go out all over the city. This makes the power in Team Rocket's suits to go out. There are also some Pokémon at the Pokémon Center who are in critical condition and if the power doesn't come back on soon, the Pokémon will get worse. Ash and his friends decide to go to the power plant to try and get the power back on. They ask Officer Jenny for directions to the plant and Pikachu comes out of the nearby bushes. Misty realizes that PIkachu is afraid that they won't come back for him later, so Ash decides that Pikachu can come with them. Pikachu jumps into his arms and shocks him while the shadowy Pokémon watches him from a bush.
They enter the plant and no one is there to greet them. Misty looks at a map for directions to the central control room. Misty freaks out as something flies behind her. Ash says that Misty is a coward and Misty and Brock see the shadowy figure behind Ash. Ash turns around and no one is there. The shadowy figure goes behind Pikachu and Ash scans it with his Pokédex. It turns out the shadow is a Magnemite. Ash tries to catch it, but Magnemite is only interested in Pikachu. Magnemite appears to be in love with Pikachu.
Ash yells at the Magnemite to leave and it does. A really bad smell enters the hallway. They turn around to see a grate fall off the ceiling and a group of Grimer fall out of the ceiling. Brock thinks they shouldn't say anything that would insult the Grimer, or they will attack. Ash compliments them on their smell, but Misty says that they stink. The leader of the Grimer, a Muk, approches them from behind and the Muk orders the Grimer to attack Ash and his friends. Ash and his friends start to run away from the Grimer and the Muk. As they run around the corner, they meet two plant workers. The Grimer start catching up to them and they all run into the control room for safety. One of the workers explain that the Grimer are clogging the pipes to the sea and preventing the power from coming back on.
The Grimer break down the door. Pikachu uses ThunderShock to stop the Grimer, but it doesn't work. The Magnemite from earlier bursts out of the grating, followed by some other Magnemites and Magnetons. Their attacks scare away all the Grimer. The Magnemites and Magnetons also scared away the Grimer that were blocking the pipes to sea and the power comes back on.
But, the Muk still remains. Pikachu uses ThunderShock on it and the Magnemite that likes Pikachu uses ThunderShock on Muk as well. The attacks make Muk faint and Ash catches it. Much to Ash's disappointment, the bad smell goes through the Poké Ball!
Everyone leaves the power plant and the sun has come up. Pikachu has stopped being magnitized. One of the workers explains that when an electric mouse has too much electricity, it becomes magitized and it acts like it has a cold. The Magnemite doesn't like Pikachu anymore because it only liked Pikachu because it was magitized and Magnemite doesn't have an interest in an unmagnitized electric mouse.
Team Rocket's Gyarados submarine rizes up out of the sea and it has a big magnet on it. Their plan is to catch Pikachu using the magnet since Pikachu is magnitized. But they don't know that Pikachu isn't magnitized anymore. When they turn the magnet on, all the Magnemites and Magnetons all over the city get stuck on it. The weight of the Pokémon is so heavy, that the submarine sinks to the bottom of the sea.
As Ash and his friends are about to leave Gringy City, they tell everyone that the Grimer being here is a sign that the city is too polluted. The citizens promise to clean up the city.
Meanwhile, at Professor Oak's lab, a Poké Ball arrives from Ash. Professor Oak is curious what Ash has caught and he covers his nose as Muk appears.
- Ash catches a Muk, but he sends it to Professor Oak's lab because he can't stand its smell.
- At the end, when Ash is talking to Nurse Joy, the Raticate and Fearow are way smaller than their usual sizes.
- In one scene, Pikachu's ears are much bigger than they normally are.
- The "Who's that Pokémon" in this episode was Magnemite.
- Though Ash had six Pokémon, he decided to leave Muk with Professor Oak.
- Ted Lewis provides the voice for one of the two power plant workers.
- Ash: "Excuse me, miss, but are you the oddball of your family?"
Nurse Joy: "Oh no, it's all my other relatives who are odd."
- Misty: "And you call me chicken! You're a total coward!"
Ash: "Maybe not a total coward."
- "The smell goes right through the Poké Ball."
Ash about his new Muk.
- Jessie: "Now the fun begins, with our new secret weapon. Tell them James."
James: "Now that Pikachu is magnetized, our plan is to take this high powered electromagnet and..."
Jessie and James: "...finally capture Pikachu!"
Meowth: "Hey, who're you talking too? Let's just catch Pikachu."
Jessie: "Why don't you keep your sniver box to yourself?"
James: "That's right."
Professor Oak: "What is that smell?"
- "What's the idea of sending me a Muk?! YUCK!"
Professor Oak about Ash's Muk.
Watch this and other episodes: Pokémon Episode 30: Sparks Fly for Magnemite