Continuing their journey to Virbank City and Ash’s next Gym battle, our heroes are startled to run into a Vanilluxe, and its Trainer, their friend Georgia. She tells them she’s on her way to a laboratory called Ferroseed Research, run by a Professor Malveaux, to get moss grown there that is reputed to improve the skills of Pokémon, and our heroes go along with her.
Once there, they meet one of Professor Malveaux’s assistants, Case, who gives them a tour of the facility. They learn how the research conducted on the Ferroseed helps them to learn how to utilize the many kinds of moss the Ferroseed produce. Suddenly, three Ferroseed who have been absorbing electricity from charged stones start to wildly produce moss that overtakes the research center, and growing so fast it threatens the whole city!
Making Ground- and Electric-type Pokémon sick (including Pikachu), the moss continues to grow out of control. When Iris, Axew, Oshawott, and Georgia’s Vanilluxe get trapped on the roof of the research center, Vanilluxe’s Icy wind eliminates a large part of the moss. Professor Malveaux quickly theorizes that Ice-type moves can stop its spread. With the help of Vanilluxe, Georgia’s Beartic, and Pikachu (who has been cured, thanks to an antidote Professor Malveaux formulated) manage to stop the moss from spreading, and the city is freed from the danger.
After Professor Malveaux thanks our heroes and Georgia for their help, Georgia says goodbye and our heroes board a ship headed for Virbank City.