While Ash and his friends stop for lunch, they are particularly keen to find out what Pokémon will hatch from the Pokémon Egg. Just as Brock suggests it's going to be a Legendary Pokémon, the Egg begins to glow as if it is about to hatch, but it's only a false alarm. As Ash tries to persuade the Egg to hatch by tucking it under his shirt and singing, Team Rocket spies on them from the bushes and then begins to scheme how to get it. At that moment, the Egg begins to glow again from under Ash's shirt. When Ash pulls his shirt up, it reveals a sleeping Larvitar. Ash checks his Pokédex for more information, and while he is disappointed to learn that it isn't Legendary, he admits that it was cool to see it hatch. Misty notices that Larvitar isn't moving terribly much, and Brock checks its temperature to discover that its body temperature is way too low. The trio decides it's best if they get Larvitar to a Pokémon Center, and promptly go to a nearby one.
Nurse Joy can't find anything wrong with Larvitar so she decides to call Professor Elm to alert him to the situation. However, Elm fails to reply because he is busy hosting Professor Oak and Delia, who have traveled to New Bark Town so they can see Ash off to the Silver Conference. Trouble is brewing back at the Pokémon Center: not only can Nurse Joy not get a hold of Professor Elm, but a storm is brewing and Larvitar isn't getting any better. As Nurse Joy finds that Larvitar is getting worse, the power goes out. Nurse Joy goes to check on the generator but falls down one of Team Rocket's pitfalls. Jessie explains to her that they were the ones who damaged the generator and now they're going to kidnap Larvitar. Inside, Ash and his friends wonder where Nurse Joy is. Jessie, dressed up as Nurse Joy, and James, disguised as a surgeon, tell them that they need to take Larvitar to the hospital. Ash almost complies, but Brock stops him and tells him that it's clearly not Nurse Joy. Brock explains that Nurse Joy usually has a sweet-sounding voice and doesn't smell like dirt. Jessie is immediately insulted and takes off her face mask to reveal herself. Meowth smacks Jessie with a paper fan for blowing their cover. James tries to take Larvitar by force, but he only pulls off its warm blanket. Ash orders Pikachu to use Thunderbolt, sending Team Rocket running off. Misty and Brock go rescue Nurse Joy from the pitfall, but Nurse Joy explains that the generator's blown beyond repair. Inside, Ash uses Cyndaquil to heat Larvitar with the flame on its back.
Back in New Bark Town, Professors Elm and Oak are having an intense dinner table discussion over the environment and its effect on a Pokémon’s nature. Elm evidences the Red Gyarados, though Oak disputes his claims. Delia is hoping the debate will end when she notices something on Elm’s computer. Elm finally responds to Nurse Joy's email about Larvitar, and immediately hits the road to the Pokémon Center with Professor Oak and Delia. The following morning the two Professors and Delia arrive at the Center. The Professors tell them that they'll take care of Larvitar while the others eat breakfast. The Professors manage to get Larvitar's body temperature up and make it conscious, but Larvitar still doesn't respond to external stimuli and it hasn't eaten, making it obvious a problem still exists. Just as Delia calls everyone away to eat breakfast, Larvitar opens its eyes slightly.
At the table, Ash tells the others of a dream he had the night before where he saw into the eyes of Larvitar as an Egg. The Egg was tossed around in traffic and rolled under the feet of people on a sidewalk. Professor Elm declares that this must be the cause for its unresponsiveness. Ash asks Professor Elm if he can take Larvitar outside for a while, and Elm says it's alright to.
Outside, Ash shows Larvitar how great the world is, showing it a field, the ocean, and the sky, but as Larvitar takes it all in, Team Rocket shows up and invites Larvitar to come lay on a pile of hay with them. After Ash tells them that Larvitar won't, Team Rocket dives into the hay and comes out with a vehicle with a pair of arms and a giant net on it. The arm grabs Ash, who drops Larvitar in the process. Before Team Rocket can steal Larvitar, Ash tells Pikachu to get Larvitar away, but Larvitar won't move. Pikachu tries to zap the vehicle, but it's shockproof, and Team Rocket grabs Pikachu with the other hand. With the net, they go for Larvitar, but a herd of Jumpluff gets in the way. As Larvitar watches the Jumpluff being swatted away and hitting the ground, it remembers bouncing through the streets as an Egg and uses Screech. The shrill sound forces everyone to block their ears. Ash tells Larvitar to run, but instead, it uses Hidden Power to levitate the vehicle and free Pikachu and Ash. The Professors, along with Brock and Misty arrive in time to witness Larvitar's incredible power, and they are left in shock as it sends Team Rocket blasting off.
Ash congratulates Larvitar and tells it there's nothing to be afraid of when it's with its friends. Larvitar begins to smile as it watches some Bellossom dance, as well as a flock of Pidgey and Butterfree fill the sky. Ash offers Larvitar some more assurance, though the new hatchling instantly cowers in fear when Misty greets it. Elm, on the other hand, is not concerned by Larvitar's shy nature and admits that it will be some time before it truly opens up.
The group later returns to New Bark Town where Ash registers for the Silver Conference at the local Pokémon Center. In the evening, they venture over to Elm's Laboratory. Delia wishes her son all the best. Professor Elm also entrusts Ash with Larvitar, explaining that it must be delivered back to Mt. Silver, where the Egg was originally found. Misty is concerned that the travel may be too much for Larvitar, though Elm and Oak reply that it will be best for it to return to its home and develop along the way. Ash formally asks Larvitar if it would like to travel, and the young Pokémon happily agrees to join the group. Misty, however, is unimpressed and comments that this is so typical. Ash accepts the task and places Larvitar inside his backpack as he and his friends leave for Mt. Silver.