The Mystery Menace is the 21st episode in the Orange Islands season.
Ash and co. climb over a mountain and notice the city of Trovitopolis. Team Rocket tries (and fails once again) to trap our heroes, however they do fall into the Trovitopolis Sewer System. There they find a monster and who should save them but Officer Jenny, unfortunately they wake up in a jail cell. They were put there by the Mayor of Trovitopolis, even though they were only wandering around the sewers for Ash's Bulbasaur. What is the conspiracy the Mayor is trying to hide, and why would the sewers be off limits?
The "Who's that Pokémon?" of this episode is Zapdos.