Brock has gone his separate ways with Ash and Misty and is now at Pewter City. He comments on how good it is to be home. Flint is in disguise again and he tells Brock to leave. Brock takes the disguise off him and wonders why his dad wants him to leave. Flint tells Brock to remember the times when the gym was perfect and was a good place for rock Pokémon. Then Flint tells Brock that his mother did something to the gym. Brock looks at the gym is shocked to see that flowers surround the gym. Flint tells Brock to go home.
Brock opens the door to his house. His brothers and sisters say hello to him. Brock's mom, Lola, is finishing putting a painting on the wall. She asks Brock's opinion on the artwork. Brock didn't even think it was art. Flint appears behind Brock. They look in the inside of the gym and Brock is shocked to see water and other decorations in it. Suddenly, water Pokémon such as Tentacruel and Gyarados pop out. Brock is very disappointed. Brock wants his mom to get the water Pokémon out of the gym. Even Brock's sisters and brothers don't like it. Brock tells Flint to do something. Flint says that nothing works and that he's tried everything. One of Brock's brothers says that they should fight for the gym. Brock agrees and he wants Flint to battle Lola for the gym.
Brock tells Lola the rules. Lola thinks that Brock is just being stubborn and Brock yells at her. Lola agrees to battle but if she wins, Brock's brothers and sisters have to become water Pokémon trainers. One of the brothers says that Lola uses water Pokémon and that Flint has no way of winning because he only uses rock Pokémon. Flint agrees and Brock lectures him that he's a gym leader. Then Brock tells Flint a story about Ash and that there is always a way to win a battle. Brock agrees to be the judge. Lola sends out Marill and Flint sends out Golem who wobbles on a rock. Flint tells Golem to use Earthquake. The water on the gym floor toughens up and Marill starts to lose control. Marill falls into the water but Lola commands Marill to use Surf. The water takes Golem with it. Golem sinks down to the bottom. Lola tells Blastoise to bring Golem up to surface. At the surface, everyone helps bring Golem back to life.
Flint congratulates Lola for a well battle. Flint remembers the day when he first met Lola. It all started with a Pokémon battle and Lola beated Flint. They both hold hands and smile at each other. Brock still won't let go of the gym.
Everyone is in the kitchen. Brock is cooking something and his little brother starts to talk about the girls in his school. Meanwhile, Flint and Lola are talking to each other in the gym. Flint thinks that Lola was getting bored of him but Lola tells him that she loves him more than anything. At the table, Flint and Lola start to do some "things" such as feeding each other. Brock wants to change the subject and talk about the gym. Lola comments Brock on his cooking and she tells him that the food is delicious. Brock wants to know when he can battle Lola for the gym. Lola tells Flint to tell Brock about it. Flint and Lola start to play with each other when Brock starts to yell. Flint decides to make the announcement. He tells everyone that the Pewter Gym will now hold water and rock type Pokémon. Forrest (Brock's brother) doesn't like the idea and he runs away. Brock's sister tells Brock that Forrest wanted to become the gym leader when he grew up.
Brock sees Forrest looking at the ocean and he joins him to talk. Forrest asks Brock if he has met a lot of girls. Brock says yes but he also says that he has to stay focused to be a Pokémon Breeder. Forrest tells Brock about what he wants to do. Then Forrest tells Brock that he wants to be a great rock type Pokémon trainer. The thing that Forrest worries about is losing to water type Pokémon. Brock tells him that he'll beat the water Pokémon.
The next day, Brock comes up to his parents. Flint shows Brock the new sign he made for the gym. Brock says that it won't work and that he wants to fight Lola today. Lola agrees to battle Brock. Flint tells them that he'll be the judge for the battle. Brock sends out Onix and Lola sends out Mantine. Brock tells Forrest to watch the battle closely and he commands Onix to use Dig. The water in the gym begins to drain out because of the hole. Then Onix comes up and hits Mantine. Mantine regains its strength and hits Onix with Bubblebeam. Brock tells Onix to use Bind and Onix squeezes Mantine hard. Lola tells Mantine to use Confuse Ray but it doesn't respond. Then Lola tells Mantine to use Bubblebeam. Mantine scores a direct hit and Onix lets go. Mantine uses Bubblebeam again and hurts Onix. Then Brock tells Onix to use Slam on Mantine really hard. Onix scores a direct hit on Mantine and Mantine faints.
Lola recalls Mantine back and tells Brock that he can keep the gym. Forrest comes up to Brock and congratulates him. Then Brock tells Forrest that he can keep his Onix so that he can have a Pokémon of his own. It's now time for Brock to leave. Forrest tells Brock that they are going to have a battle once Brock comes home again. Brock then says that he's going to travel back to Hoenn. The whole family waves goodbye to Brock as he departs for Hoenn to meet up with Ash.