As they continued their journey, Ash and his friends go through the Ice Cave, a shortcut to Blackthorn City. However, suddenly they slip and fall into a hole dug by Team Rocket.
Team Rocket then starts putting water in the hole. Ash's Pikachu uses Thunderbolt and Misty's Politoed uses Water Gun sending Team Rocket blasting off. When they finally got out of the hole Brock seems to have caught a cold.
As they walk along, they find a Pokémon Center. There are no Chansey here, instead Jynx appear. As they check Brock's temperature, he becomes feverish because of Nurse Joy, who explains that she is the sister of the Nurse Joy who appeared in The Joy of Pokémon. Joy sees Brock's fever worsening, and he remains in bed under the care of Jynx as Joy explains that the ice cave remains stable due to a large building acting as a refrigerator.
Meanwhile, Team Rocket, overlooking the Pokémon Center from a nearby cliff, complain about the cold draft. They leave to find its source and soon come upon the large building Joy described. They set about their evil deeds as the scene cuts back to Brock in the Pokémon Center.
Brock continues to dream of Nurse Joy, and mistakenly shares a kiss with Jynx as it cares for him. Nurse Joy notices a rapid rise in cavern temperature, and goes to the building with Ash and Misty to investigate. All three travel by sled driven by Piloswine.
Upon their arrival, the trio see that the structure has been reversed, heating the cave and cooling the jungle outside. This puts both sides in danger, so the group run outside to find the cold air pipe, but immediately fall into a pitfall dug by Team Rocket.
Team Rocket tell Ash, Misty and Joy their plan to steal the Ice-type Pokémon before running off. The group climb out of the hole with help from Bayleef. Knowing they have to get the pipe back in the cave, Ash commands Bayleef to use Vine Whip to grab the pipe. They then pull on Bayleef's vines as hard as they can, and the pipe is restored to its original place.
The scene cuts to Brock lying in bed in his sickly state, and he gets up out of bed. He notices Team Rocket outside the Pokémon Center, and they have set up a bunch of heaters to weaken the Ice Pokémon there. They scoop up all the Swinub and Piloswine there, and then, Jynx appears. It attempts to stop them, but Team Rocket points a heater right at it, and Jynx collapses.
Brock, in his weakened state, appears to confront Team Rocket. Brock sends out his Geodude, while Jessie sends out her Arbok. Geodude uses Mega Punch, but this has no effect on Arbok, and the snake Pokémon retaliates using Headbutt. Geodude is sent flying into Brock, and Jessie commands Arbok to use Wrap on both of them. Arbok wraps them with its tail and slams them into the ground. Brock has been defeated, and Team Rocket proceeds to steal Geodude.
Just then, Ash, Misty and Joy appear. Misty and Joy tend to Brock, while Ash takes care of Team Rocket. He sends out Totodile, and Jessie once again uses her Arbok, and James sends out Victreebel. Misty joins in too, and she sends out her Corsola. She commands it to use Headbutt, and James, under attack from Victreebel, is sent flying. Meanwhile Totodile uses Bite on Arbok. Jessie then sends out Wobbuffet. Corsola uses Headbutt on Wobbuffet, but it uses Counter and sends Corsola flying. Totodile uses Water Gun on Wobbuffet, but it counters this too and Totodile and Corsola are defeated.
Meanwhile, the cold air enters the battleground. Pikachu then uses Thunderbolt on the heaters, and the Ice Pokémon are revitalized. Jynx and Piloswine use Blizzard on Team Rocket. Joy commands Jynx to use Lovely Kiss on Wobbuffet. For their final effort, Joy commands Jynx and all the Piloswine to use Blizzard at full power, instantly freezing Arbok, Victreebel, and Wobbuffet. Pikachu then delivers the final blow using Thunder, blasting off Team Rocket.
Later, Nurse Joy thanks Ash and company for helping her to save the Ice Pokémon, and Brock's fever is now gone. Ash, Misty, Brock and Pikachu leave Joy and the Ice Cave Pokémon Center.
They have now arrived at the end of the Ice Cave, and they come across Blackthorn Lake. Brock informs Ash and Misty that Blackthorn City is on the other side of the lake, and our heroes rushes towards Blackthorn City and Ash's final Johto League Gym Badge.