The Mystery Menace is the 21st episode in the Orange Islands season.
The episode begins with Ash and his friends still taking on journey. Ash is still hungry tough, Tracey calls Ash and Misty to climb and find that they're in Trovitopolis, the largest city the largest city on Mandarin Island South.
Meanwhile, The Team Rocket, who are up in the hill, spy the heroes. Their known plain that the heroes are acutally standing a trap and had a dynamite inside, as well as caputaring Pikachu. The group prepare to actiave the trap. However, it dosen't and soon realizes that they behind trap. And they fell soon and soon collapes the heroes they stand in.
The heroes finds that they fell into cave, they begins to find search escape of the cave. Whilst they search, they find tunnel and hear bell ringing sound. The find plant comes out of Ash, he belives think that is in his shoulder. Only to find, that Pikachu is not in his shoulder. The groups soon fear and screams as they see vine appears in the larger form. Ash sends Pikachu to fights, but does stand fight with him. He then sends Bulbasaur for fight, however, a vine caputre Bulbasaur and drags him in water sewer. Much to Ash's dismay, Ash tries to jump in water to Bulbasaur. But Officer Jenny shows up to say that this place is dangerous and force them to get out (altough Ash still refuses and wants to save Bulbasaur, but Misty and Tracey tie him up).
The scene cuts that the heroes are in inprisonmed. Officer Jenny arrived (slaming Ash in the door, who was still bangs on the door) told the that they're free to go. The Major arrives and tells him that she cannot releasing heroes. Jenny told Major that they're arrived in the town and are going to Pokemon Gym on Trovita Island. The Major agree with it, and forbis the creatues tough the sewer. The Ash still wants wanted to save Bulbasaur he had captured. The angers The Major who forces the group to be arrseted for endangering public safety. Jenny there is the how to get inside is 500 miles of sewer under the city, and over 5,000 manholes. The snaps Major for too forbidding for safety. He also tells that he well get election next week. The Nurse Joy bursts in to tell Major that she heard what sewer create problem is. The Major soon force the plan to send SWAT team down to the sewer's to destory it.
The "Who's that Pokémon?" of this episode is Zapdos.