When Brock's Mudkip evolves into a Marshtomp, it accidentally injures a Flaaffy with a wayward Mud Shot. Brock apologizes profusely to Flaaffy's Trainer, Mariah, and offers to go get some medicine, but Mariah has a better idea. She takes our heroes to meet her grandmother, Katie, whose specialty is making Pokémon medicines that are in big demand by Pokémon Trainers everywhere. This of course includes Team Rocket...although their only demand is to steal everything they can from Katie, including her entire medicine supply! They're unsuccessful, thanks in large part to Katie's other employee, a young man named McCauley, who displays surprising courage when he teams up with Mariah to stand up to Team Rocket. Katie, much impressed with her two brave employees, decides to retire and let them take over the business. In the process, Mariah and McCauley discover that they have feelings for each other--much to Brock's disappointment!