Our heroes make their way to Cattailia City, a town recognized for its magnificent buildings. A patrol car barrels down the street, and knowing that Officer Jenny must be inside, Brock gives chase. However, a few seconds later, he trips over a thin web. Ash and Misty catch up with him and after Togepi notices something approaching, a Spinarak appears. Mistaking it for another Pokémon, Misty walks toward it, until she realizes that it’s actually a spider.
In another part of town, Team Rocket breaks into a storage building. Dressed in odd uniforms, Jessie commands Meowth to pick a lock. Instead, he breaks his claw. Jessie tells Meowth that the Black Arachnid could break through thousands of locks while Meowth can’t even open a single one. Using a lock pick, James enters the building. Inside, Team Rocket takes a small bowl. Suddenly, a patrolman spots them, but James hurls bottle caps at him as they make their getaway.
The police arrive at the crime scene a few hours later. An officer tells Jenny that they have apprehended the thieves. They approach Ash, Misty, Brock, and Pikachu, who are caught in a giant ball of web. Jenny lets them go and explains that they mistook them for the Black Arachnid, a thief that terrorized Cattailia over a hundred years ago. Jenny notices Pikachu and Togepi and asks the team if they’re the professional Pokémon crime fighters her sister from New Bark Town told them about. Ash complies, and asks why the police force uses Spinarak instead of Growlithe. Jenny explains to him that it’s traditional to use Spinarak in Cattailia City. A long time ago, the Black Arachnid ransacked the town. He was known for his "stealthiness" and his professionalism. Accompanied by a Meowth, they used Pay Day to scare the police off whenever it seemed like they were about to get captured. However, the Black Arachnid was stopped thanks to the efforts of the Officer Jenny from 8 generations ago and her Spinarak. Using its web, the Spinarak stopped the Black Arachnid dead in his tracks. Jenny says that her Spinarak is the same one that caught the Black Arachnid over a century ago. Ash volunteers to capture the thieves because it’s wrong to use Pokémon for criminal acts.
On top of the clock tower, Jessie devises their next plan. Afraid of losing his bottle cap collection, James scolds Meowth for eating out of the bowl they stole. Jessie suggests that instead of stuffing his face, Meowth could be learning Pay Day. Suddenly, she gets an idea. She’ll send a letter telling the police what they’re going to steal, and while the they send guards to patrol the site, Team Rocket will take the item from under their noses.
The police receive Jessie’s letter, and they learn that the Black Arachnid is planning to steal the mayor’s prized trophy at midnight. Jenny convinces the mayor to let the team handle it, and he gives it the ok. Ash sends out Squirtle, Bulbasaur, Charizard, and Heracross to stand guard. Squirtle dives into the pool. Bulbasaur goes into a flowerbed. Heracross climbs up a tree, and Charizard pretends to be a statue stationed next to a Blastoise fountain. Spinarak also helps by creating webs around the perimeter.
A few minutes before midnight, Ash struggles to stay awake. The clock hits twelve, but the Black Arachnid doesn’t show up. They mayor rushes in and gives the group a giant meal to celebrate and congratulate them. After they finish eating, the lights go out. Team Rocket appears from the ceiling. Ash asks how they got in, and they explain that they hid in the attic all day. He then asks why they didn’t show up at midnight, and Meowth tells them they fell asleep. James uses Pay Day and escapes with the trophy. Team Rocket gets away in their balloon, but Spinarak’s net stops them. Squirtle uses Water Gun, followed by Bulbasaur’s Razor Leaf. Charizard burns the web with a Flamethrower. Team Rocket’s balloon spins out of control with the trophy still in their possession. Spinarak shoots a steam of web to stop Team Rocket, while Charizard Tackles the balloon and makes a cache of loot fall. Ash tells everyone to catch something. With everyone’s hands full, the trophy has yet to be saved. Ash dives in to intercept it, but Spinarak suddenly shoots out a web to catch the treasure, finishing the job.
The next morning, Jenny reports that everything that was stolen has been returned to their rightful owners. She wishes the team the best of luck as they head out of Cattailia. Meanwhile, Team Rocket sobs over their loss. Jessie blames James and Meowth for messing things up, and everyone gets into a brawl.