In the start of the episode the narrator foreshadowes the days adventure by describing Ash, Misty, and Brock's current location in the desolate factory in Gringy city. A shadowy town where even the sea breezes smell terrible. Ash and company are walking along the docks when Ash openly ponders why the place has so many factories and so few people. Brock explains that the town used to be a busy local of activety, but the pollution from all the factories hurt the nearby ecosystems. Just then Pikachu begins to look dazed and lets loose an electric shock that hits its nearby trainer. Around the corner a Magnemite lurks in the shadows.
Ash holds the weary electric mouse close to his body as they hurry to the town's Pokemon Center. Meanwhile, Meowth watches this departure from far away with Jessie and James. Half way through their plotting they erupt in an invisible pain about the smell of the sewers. Meowth calms them down by giving them suits to ward off the horrible stench. Relucantanly they use these suits to swim through the polluted sewers of the city to the Pokemon Center, obviously up to no good.
Ash calls out for Nurse Joy as they enter the Pokemon Center. Yawning, the town's Nurse Joy appears, casually trying to convince that Pikachu has nothing but a cold. Its random electric sparks prove otherwise. Ash calls out Nurse Joy, telling her that all her other relatives were so much more helpful. The Nurse Joy seems unphazed and continues to describe her diagonsis. Clearly, she is the black sheep of the Joy family.
Across town, the power plant in the town goes haywire, shutting down all electricity throughout the city. The plant workers struggle helplessly to try to find the solution to the problem. Meanwhile, Meowth panics at this sudden loss of power. WIthout it, there is no air pumping to the scuba suits that James and Jessie currently inhabit. The two criminals slowly sink to the bottom. Things are even worse at the Pokemon Center, where the Pokmon in intensive care are suffering without electricity. Ash, Misty, and Brock run off to try to fix the issue.
Their first destination is Officer's Jenny office, where they discover the location of the Power Plant. Its at this time that Pikachu stumbles out of the bushes, still fatigued. It followed Ash because it was afraid that they would leave it behind. Ash decides to bring Pikachu along as long as Pikachu agrees to take it easy while on their mini adventure. As they head towards the plant we see that Meowth was successful in rescuing his criminal cohorts. They notice Ash, Misty, and Brock go by and ready their next plot to steal Pikachu.
The three enter the darkened plant. They look at a map in order to find the main power room. As they travel around the empty hallways, however, they discover that they are not alone. Shadowy Pokemon levitate by in silence. Finally, a figure drops down infront of the group. When they turn around another shadow is behind Pikachu, who is crying out for help. Magnemite, a magnet Pokemon. Its means of floating through the air are not understood. This very mysterious Pokemon is of the electric type. says Dexter. Misty instantly believes that it is Magnemite who is causing the power loss. Ash, realizing that it is a Pokemon, wants to catch it.
They watch as it circles Pikachu in the air. Brock explains that this Magnemite seems to have some kind of affection for Pikachu. Ash yells at it to force it away from his Pokemon. After this though, a terrible smell wafts through the air. A vent drops down, several purple piles of sludge falling to the floor as well. Grimer, the sludge Pokemon. Born from sludge, these Pokemon specialize in sludge attacks. Ash and Misty both complain about the burning in their nostrils, only to further anger the army of Grimer in front of them. In response, a Muk towers over its fellow sludge Pokemon. Muk, Grimer's evolved form. Use extreme caution as its sludge form contains poison..
Muk commands several Grimer after them and the three traveling companions take off running. They run into the two Power Plant workers as they round the corner. Before they can officially introduce each other though they sprint away, still being followed by the poisonous Pokemon. They just barely manage to slip into the control room. Ash immediately requests an explaination. The Power Plant workers explain that the Grimer are clogging the sea water intake that power the generators. Suddenly, the Grimer begin to ram the door open. With no where to run they have to fight.
It is up to the sick Pikachu to take on all the opponents. Pikachu unleashes its Thundershock on one, but more seem to take its place. Just when all seem lost several dozen Magnemites and Magneton fall down through the vents. Brock assumes that they must be friends of the Magnemite that likes Pikachu. They all combine their electric attacks to send the Grimer away. The sludge Pokemon retreat, opening up the water way again, and allowing power to return to the city. But Misty notices that the adult Muk is still left. Pikachu attacks it with a thundershock, but it resists. The affectionate Magnemite steps into aid its crush, letting loose an electric attack of its own. Ash tosses a Pokeball at the weakened Muk, leading to a successful capture.
However, the stench is so strong that it even manages to seep through the pokeball. On the good side, Pikachu has recovered. One of the power plant workers explains that an electric type Pokemon can become sick if it stores too much energy, causing its body to become magnetized. It appears that this was why the Magnemite was interested in Pikachu because now it seems it couldn't care less. But the trouble isn't over yet. Team Rocket appears in a large Gyarados submarine, a gigantic magnet strapped to the top. They plan to use this device to capture the magnetized Pikachu. Unlucky for them they capture several scores of Magnemite and Magneton instead. This increase in weight causes their vessel to seek to the depths of the water.
Ash, Misty, and Brock say their good-byes to the Nurse Joy and Officer Jenny of Gringe City. Nurse Joy says that they have inspired her to be a better nurse than she had in the past. They all decide that they need to take better care of the pollution levels. All the way back in Pallet Town, Professor Oak curiously recieves Ash's newest capture. Wondering what it could be the Pokemon opens to reveal the large sludge Pokemon, Muk. Oak complains loudly as the episode comes to a close.