Ash and his friends are on their way back to Ecruteak City to get to Mahogany Town. On their way down a hill, a couple of milk cans start to roll down. They break into a run until someone says to catch them so they stop and grab them. They carry the cans up towards a truck driver who asks where they're going. Since the gang helped out with the cans, the driver says he'll give them a ride along the route to a destination closer to Ecruteak. They get to an airport with a blimp waiting. Team Rocket is later spying on them, seeing if there would be a way inside the blimp. They sneak onto the cargo hold and look around. They come to a freezer and decide to go in, except the door latch closes on them when they go in. After a while, they notice the door is stuck, and by the time they knock it down, they're frozen. Since the blimp is making another ascent, they slide out of the blimp.
After they land, Ash gives Professor Oak a call at a nearby rest house, except nobody's there when he calls. Mimey pops up eventually, followed by Ash's mom. Ash wonders what's going on when Oak and Tracey come into view. It looks like they're having a little problem with the Pokémon in the area. Three different groups of the Oddish evolutionary line, the Hoppip evolutionary line, and some Water-type Pokémon won't cooperate with each other in order to share a lake. Oak suggests to Ash that he should send Bulbasaur to them because Bulbasaur might be able to help out. Ash does so and hopes that Bulbasaur could solve the problem.
Tracey, Oak, and Bulbasaur set off to the lake. Along the way, Heracross comes by happily and yet again sucks Bulbasaur's bulb, resulting in Bulbasaur whipping Heracross with Vine Whip. After arriving, Bulbasaur rushes up to the three groups of Pokémon. Bulbasaur tries to talk them into sharing the lake and also puts a Bellossom in front of a Jumpluff, but instead gets slapped by the Bellossom. Afterward, it tries to move a Jumpluff in front of a Poliwhirl, but gets Tackled by the Jumpluff and slapped by the Poliwhirl. This continues on until all three groups turn on Bulbasaur and start a fight. Tracey tries to help by sending out his Pokémon but the fight ends up with Bulbasaur releasing a Solar Beam straight up into the sky. Stunned, all the grass Pokémon respect Bulbasaur and each other.
After the quarrel is solved, Bulbasaur decides to get to work. Oak and Tracey stand by to watch, Tracey taping the whole event. Bulbasaur and Marill show the grass types a blank field, then cut the grass to make a patch of barren land, and started to dig up the sand. The others got the idea and started to dig in the clearing. After a while, Bulbasaur hit something hard, hard dirt which they can't dig through. Bulbasaur runs off towards the Poliwhirl from before. The Poliwhirl declines for a while, but Bulbasaur persists. Eventually, the Poliwhirl agrees. Bulbasaur later talks with a Sandslash; the Sandslash also agrees to help out with the problem.
Soon, all the Pokémon are working on creating a new lake. Ash's mom and Mimey come by later, both with bags of Pokémon food for the Pokémon. Later, one the Sandslash encounters a boulder in the ground. Once they expose enough of it, Bulbasaur tries to remove it. After a while, all the other Pokémon start to help out Bulbasaur. The boulder is carried out and everyone resumes their work. Soon enough, the Sandslash start scattering because they hit the ground water. The hole fills up with water, creating the lake! But the ground loosens and falls where an Oddish by the boulder was. The boulder is just about to land on the Oddish but Bulbasaur pushes it out of the way... except Bulbasaur can't get out, and the boulder is about to land on Bulbasaur! Professor Oak, Tracey, Delia and all the other Pokémon watch in horror as the boulder lands.
We then see a flashback of Bulbasaur's travels which show how, despite its initially distrusting nature, became a valuable part of Ash's team. We see some of the adventures Bulbasaur has had while traveling, as well reminding us of how close Ash and Bulbasaur are.
Later in a field, Ash wakes up from a nap. He looks towards the clouds and senses only that Bulbasaur is doing well.
Oak and Tracey push the boulder into the flooded area, but Bulbasaur is nowhere to be seen. Everyone starts to wonder what happened to it, but then Bulbasaur digs out from the ground, alright and ready to go! Tracey marvels that Bulbasaur cannot usually learn Dig, but Oak notes that in times of need, it is possible to call upon power never known to it previously.
Ash gives Oak a call again to see how things are going. It looks like Bulbasaur was a great help, however whenever it leaves the other Pokémon go right back to fighting. Oak asks if Bulbasaur can stay and keep things in check. Ash gets sad at the thought of losing Bulbasaur, having had it almost as long as he's had Pikachu, but he knows that this is much more important and asks Bulbasaur if it is okay, and Bulbasaur agrees. With that, the decision is made that Bulbasaur will remain at Professor Oak's lab for good. As Ash continues on his journey through Johto, Bulbasaur begins his new duties in Kanto. After breaking up a squabble between a Gloom and a Skiploom over an apple Bulbasaur looks up to the sky, thinking of Ash and knowing he'll be just fine.