Mariah works with her grandmother, Cadee, and McCauley, who make healing potions using electricity. She came upon Ash battling with Brock, and her Flaaffy got attacked by Brock's Marshtomp's Mud Shot. Brock offers to give it some medicine but Mariah politely refuses. She then carries her Flaaffy back to her grandmother's pharmacy to get healed.

At the pharmacy Brock wastes no time flirting with Mariah. It is also soon discovered that Marshtomp has a thing for her Flaaffy. Brock automatically takes this as a sign that he and Mariah are destined to be together. However, Mariah seemed to have more of an interest in McCauley than Brock.

Later, Mariah gets taken away, along with the whole pharmacy, by Team Rocket, who want all the medicine for themselves to sell. McCauley jumps into the flying pharmacy in order to save her and the medicine. Brock attempts to help out by using Marshtomp's Mud Shot to shoot down the balloon, but Team Rocket reflects it back, and the Mud Shot ends up hurting Ash's Pikachu and Cadee's Mareep. They needed the potion to make them better and fast. Both Mariah and McCauley decide to use their Flaaffy and Ampharos, respectively, to make a new batch of medicine. Afterwards, they use their Pokémon to destroy the engines on Team Rocket's balloon, causing it to crash.

After Team Rocket was defeated, Cadee felt confident enough to leave the pharmacy to McCauley and Mariah.