Upon making their way to Catallia City, Ash and his friends encounter a patrol car speeding down the street, and Brock gives chase, deducing that Officer Jenny must be inside. However, a few seconds later, he trips over a thin web, allowing Ash and Misty to catch up with him. Just then, Togepi notices something approaching, after which a Spinarak appears. Mistaking it for another Pokémon, Misty walks toward it, until she realizes that it is actually a Bug Pokémon. In another part of town, a disguised Team Rocket breaks into a storage building. Meowth tries to pick a lock, but he breaks his claw, forcing James to use a lock-pick to gain entry. Inside, Team Rocket takes a small bowl. Suddenly, a patrolman spots them, but James hurls bottle caps, meant to resemble Pay Day, 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, but they are revealed to be Ash and his friends, 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 had once terrorized Catallia City over a hundred years ago. Jenny notices Pikachu and Togepi and asks the trio if they are the professional Pokémon crime-fighters her sister from New Bark Town told them about, which Ash affirms.
Ash then asks why the police force uses Spinarak instead of Growlithe, and Jenny explains that it is traditional to use Spinarak in Catallia City. A long time ago, The Black Arachnid and his Meowth ransacked the town, using Pay Day to scare the police off whenever it seemed like they were about to get captured. However, The Black Arachnid was eventually captured by the Officer Jenny of eight generations ago and her Spinarak's web. Jenny then reveals that her Spinarak is descended from the same one that caught The Black Arachnid. Ash then decides to assist in the manhunt for the thieves. Meanwhile, atop a clock tower, Jessie devises their next plan: she will send a letter telling the police what they are going to steal. While they send guards to patrol the site, Team Rocket will stealthily take the item.
The police receive Jessie's letter, which proclaims The Black Arachnid is planning to steal the mayor's prized trophy at midnight. Ash sends out Squirtle, Bulbasaur, Charizard, and Heracross to stand guard; Spinarak creates webs around the perimeter; and Jenny, Ash, and his friends remain inside the mayor's mansion. When midnight hits, however, The Black Arachnid doesn't show up. Believing the threat has passed, the mayor rushes in and gives the group a giant meal to celebrate and congratulate them. After they finish eating, the lights go out, and Team Rocket appears from the ceiling. They announce their arrival with their motto, allowing Ash and his friends to deduce their true identities. 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 admits that they fell asleep.
James uses Pay Day and escapes with the trophy. Team Rocket flees in their Meowth balloon, but Spinarak's web stops them. The trio pulls out three large fans and continues their escape. Squirtle's Water Gun and Bulbasaur's Razor Leaf causes the balloon to start losing air, however. This allows Charizard to burn the web with a Flamethrower, causing the balloon to spin out of control. Spinarak then shoots a stream of web to stop Team Rocket. Charizard proceeds to Tackle the balloon, causing Team Rocket to blast off and their cache of loot to fall. Everyone manages to catch every last piece of the loot, while Spinarak shoots out a web to save the mayor's trophy.
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 Catallia City. Meanwhile, Team Rocket sobs over their loss. Jessie blames James and Meowth for messing things up, and everyone gets into a brawl.