The gang is lost in a forest - even Max's PokeNav shows nothing. Brock's compass shows different directions, adding it to May's fear. A Skarmory begins to chase them. May's Skitty goes out and May protects it, but in so doing, Skarmory grabs her and sends her away. Ash, Brock and Max go after it, but find two men blocking the path. They explain that nobody is supposed to go on the other side of the gate. When Ash mentiones that May's been carried there by a Skarmory, they go to speak with a man, so they follow.
May is seen to be carried on a peak. She takes Skitty back to a Pokeball and sees a Bulbasaur. Bulbasaur gets a flower, but begins to fall down, so May catches it in time. Bulbasaur is a bit taken back, but befirends May when it tickles May using a vine. However, a Sunflora, Weepinbell and a Vileplume defend it. The old man is being told the problem, but cannot help Ash, Brock and Max, as the Grass Pokemon will be angry. Nevertheless, they will go to see how to deal with the situation. Team Rocket spy so they plan to steal those Grass Pokemon. Sunflora uses Razor Leaf, Vileplume Stun Spore and Weepinbell Vine Whip on May, defending the Bulbasaur.
Bulbasaur attempts to calm them down, but more Grass Pokemon arrive to attack May. To protect herself, she sends Torchic to use Ember. Torchic negates the attacks and goes with May. Bulbasaur goes as well, but is stopped by a Sunflora. As the men discuss, Ash, Brock and Max leave to go get May. The men notice Poochyena barking, so the men spots the gang left. Brock, Max and Ash tackle the gate, but they have to climb the vines to get across. The vines break, so Ash and Pikachu are the only ones to go get May back. May hhides, but soon has to go out due to Stun Spore. The next thing she knew, she is surrounded by the Grass Pokemon. However, Ash arrives to the scene.
Pikachu uses Thunderbolt, clearing a path for them to escape. They go (with Ash explaining that the land they are on is not for humans). Pikachu uses Thunderbolt for Ash and May to pass. While their path is blocked, Torchic calls them to go near him. Soon, they stand on an edge of a cliff. The Grass Pokemon attack, but are stopped when a Venasaur comes. Venasaur checks Ash, May and Torchic - Bulbasaur that came to May seems to have warned him that they are not for any fighting. Ash and May are taken to a waterfall. Bulbasaur gives May the flower, reminding Ash of his own. Bulbasaur grabs May with a vine, going off, so Ash goes with her.
They see the forest they have been lost in before. May sees a town and explaines the Bulbasaur what it is. The old man explaines to Max and Brock that the Grass Pokemon were hunted by men, so they became enraged. To prevent any damage, some people built the gate for protection. The land has some magnetic field, preventing some mahines to work. Team Rocket begin to steal the Grass Pokemon. Pikachu uses Thunderbolt, but the attack is deflected due to the mirror. The men, Brock and Max hear the Bulbasaur being taken.
Venasaur attacks them. Team Rocket go to take it, but Venasaur uses Vine Whip and goes to take the Grass Pokeon. Meowth switches to go forwards, making Venasaur harder to take the Pokemon back. Meowth switches to backwards, so Venasaur is knocked out. Bulbasaur is taken, so may comes as well with it. Team Rocket's robot is going to be destroyed, when the Pokemon tackle the robot. Bulbasaur uses Razor Leaf, freeing all the Pokemon from the robot. The robot is about to take the Pokemon, but Poochyena from the old man use Shadow Ball, blowing the hand.
Pikachu uses Thunder, but the attack is deflected. However, Venasaur uses Solar Beam, blasting Team Rocket away. Everyone aplogises to the Grass Pokemon for disturbance and May says goodbye to Bulbasaur. However, Bulbasaur (after some thinking) goes to May, joining her.
- Featured Pokemon: Manectric, Electrike, Mantine, Electrode
- In the beginning of the episode, a classic Pokemon identification can be seen. In this case, it is a Charmander.
- The title is based on the phrase 'Mass hysteria'.
- This episode is featured on the Volume 1: Grass copy of Pokémon Elements.