On their way to Violet City, Ash and his friends have decided to take a mountainous trail, though Brock complains about how cold it is. Just then, he notices a wild Chikorita. Remembering Casey and her Chikorita, Ash loudly proclaims his intent to catch the Chikorita, which surprisingly doesn't scare it away. Ash promptly sends out Bulbasaur. Chikorita charges, but Bulbasaur counters with Vine Whip. Chikorita then uses Razor Leaf, but Bulbasaur shoots them down with its own Razor Leaf, then Tackles Chikorita. Ash throws his Poké Ball, but Chikorita simply swats it back, then catches Bulbasaur off-guard with a Vine Whip to the head.
Ash recalls Bulbasaur and sends out Charizard, though Chikorita remains steadfast. She charges at Charizard, who simply holds her off with its foot. Ash orders a Flamethrower, but Chikorita uses Vine Whip to trip Charizard, who inadvertently burns Ash. Chikorita then fires another Razor Leaf, but Charizard burns the leaves with Flamethrower, then flies in for a Tackle. Chikorita counters with another Vine Whip to the head, but this time, her vines get caught by Charizard's arms, causing both Pokémon to crash into a nearby mountain. Everyone runs over, and Ash recalls Charizard. Chikorita struggles to stand and collapses again from exhaustion. The group decides to take her to the nearest Pokémon Center. Not far away, Team Rocket watches the fight, with Jessie left very impressed by how strong Chikorita was, and believing that they need that kind of toughness on Team Rocket. However, Meowth is offended by her reasoning to capture Chikorita.
Later, Ash and his friends are approaching the Pokémon Center when Chikorita awakens. Ash reassures her, but she bites his arm. Later, Nurse Joy announces that Chikorita will be fine after some rest. She then asks if Ash is okay, noticing the bite on his arm; Ash claims that he is alright. Nurse Joy goes on to explain that the Chikorita in the area are stubborn and relentless in battle, qualities that Ash admires. Suddenly, an ambulance pulls up in front of the Pokémon Center, and two paramedics rush in. They quickly take the Chikorita's table into the ambulance, while Nurse Joy wonders who they are. They reveal themselves as Team Rocket and recite their motto, before James orders Weezing to use Smog, allowing them to escape. Ash then pursues Team Rocket.
Believing they had successfully stolen Chikorita, Team Rocket starts celebrating, but unbeknownst to them, Ash is riding on top of the ambulance. Back at the Pokémon Center, Misty realizes that Ash ran off so fast that he forgot all of his Poké Balls. Meanwhile, at a mountain cabin where Team Rocket is at, Ash and Pikachu also realize that the former forgot his Pokémon. Inside the cabin, Team Rocket tries recruiting Chikorita, but she is merely left confused. Jessie then holds up a standard Team Rocket contract, asking Chikorita to sign. James adds that if she can't write, a footprint is just as legally binding.
Ash interrupts with his own rendition of the motto, infuriating Team Rocket. Ash and Pikachu then throw snowballs and try to escape with Chikorita, but Meowth triggers a trap that ensnares all of them. Ash ends up going over a hill, and Chikorita and Pikachu are pulled down with him. They end up rolling down the hill in a snowball, bouncing off trees during their descent. Eventually, they ramp off a hill and into a tree, which eventually breaks their restraints, sending them tumbling to the ground and getting buried by snow. Fortunately, the snow hides them from Team Rocket, who are in pursuit aboard a snow-ski.
Ash and Pikachu try to figure out the route back to the Pokémon Center when Chikorita suddenly runs off. Ash attempts to stop her, but ends up slipping and falling as Chikorita disappears. Realizing it was starting to snow, Ash and Pikachu make their way to a cave and sit around a small fire they started. Ash impulsively runs out in search of Chikorita and tells Pikachu to remain inside in case Misty and Brock come. Ash eventually falls down a tunnel, where he finds Chikorita freezing from the cold. Upon seeing Ash, Chikorita jumps into his arms. He then makes his way back to the cave and ends up bundling together with Pikachu to wait out the weather.
The next day, the snowstorm stops, and Ash, Pikachu, and Chikorita try make it back to the Pokémon Center. However, they are intercepted by Team Rocket, who is using a snowball-firing machine. Chikorita uses Razor Leaf on the snowballs the trio throws, then, under Ash's orders, she Vine Whips the machine, causing it to go out of control. While Team Rocket is distracted, Ash orders a Thunderbolt from Pikachu, which causes the machine to explode, sending Team Rocket blasting off again. Ash, Pikachu, and Chikorita are then reunited with Brock, Misty, and Nurse Joy. The group returns to the Pokémon Center, and Ash and his friends prepare to hit the road again. However, Chikorita follows the group as they begin to depart and waves her scent in Ash's face. Nurse Joy explains that she wants to come along, and Ash happily accepts his newest Pokémon.