Noticing Celebi being chased by a hunter, a young boy named Yukinari comes to save the Celebi from him. And doing so, they were able to escape the hunter's Scyther and Houndoom. As they successfully escaping, Celebi then transports himself/herself and Yukinari to the future (40 years later).

Ash, Misty, and Brock meet a young woman named, Mika, and her mother, Diana. As Mika tells them about what happened 40 years ago, Yukinari and Celebi appear at the forest shrine. They all get there and retrieve them. Diana immediately recognizes that it's Yukinari (Diana and Yukinari must've knew each other 40 years ago), but Yukinari doesn't recognize Diana since, of course, it's 40 years later.

Meanwhile, an evil Team Rocket member, Vicious, steals a Tyranitar from our Celebi hunter 40 years ago, with a Dark Ball.

While taking Celebi to a pure-water lake, Ash, Misty, Brock, and Yukinari are being chased by Vicious's giant four-legged machine. Ash then encounters Vicious face to face. Ash and the gang refuse to give him Celebi, of course. Vicious's Tyranitar is then ordered to destroy them and Tyranitar starts to rampage with a Hyper Beam. Jesse and James try to help, but things don't go there way.

As Ash and friends get away, Misty's knee becomes hurt, and she collapses. This allowed Vicious's Sneasel and Scizor to catch up to them. Ash and Yukinari send out Bayleef and Charmeleon to fight off the enemy. Luckily, they were able to win against Scizor and Sneasel.

The group starts to follow an Ursaring and Teddiursa, and those two Pokemon lead them to a Stantler, which gets them to follow a Furret that gets them to the lake. Celebi goes into the water and is then fully revitalized.

After being healed, Celebi flies over to Misty, and heals her recently injured knee. Misty thanks Celebi. Ash and Yukinari agree to follow Celebi. Celebi starts using his psychic powers, allowing them to fly. Ash and Yukinari want Brock and Misty to follow, and so they do. They come to a berry tree and they all enjoy eating the berries. They start building a camp out in the forest after a tiring day. Midnight nears and Ash wakes up, seeing Yukinari sketching a picture of Celebi and Pikachu sleeping. Pikachu wakes up and follows them as they walk out. But before doing so, Pikachu wakes up Celebi, then they follow Ash and Yukinari. Amazingly, they spot a whole bunch of Metapod that are evolving. They gather up a tree to see the sparkling event from a better view.

Vicious again runs into the group, the next day, and attempts to catch Celebi once more. Vicious successfully gets Celebi trapped and he catches it with his Dark Ball!

Ash attemps to get back Celebi but fails. Vicious gets out his new Dark Celebi. The Celebi is then ordered to fight everyone off. He blows everyone away with a Psychic attack, and charges at the surrounding Pokemon with its Barrier. Vicious orders Celebi again. Celebi now uses a whirlwind, and starts picking up leaves and branches, and even starts sucking up Jesse.

Back at Mika's House, Mika, Diana, and Towa (Towa was Ash, Misty, and Brock's tourist guide in the beginning of the movie) notice the big whirlwind, and they all huddle up in Towa's boat/balloon.

Up upon the mountains, the mysterious Suicune senses the danger and dashes for the forest.

Ash wakes up after being knocked out.

Later, a huge floating spiked sphere of branches and leaves hovers towards the lake. Vicious stands at the edge of the lake. Jesse is held captive. Jesse tries to negotiate, but ends in awe. Coming up to the target point, Vicious has the core, Celebi, change the sphere's form into a Scyther looking thing. Celebi is tied down at the center of the "head" surrounded by vines and a barrier, and it seemed to have no expression on its face at all.

Towa picked up Ash and his friends and headed for the monster thing. As a test-fire, Celebi is ordered to fire at the balloon. A purple energy orb forms at the monster's mouth and fires, but only blowing off one of the balloons on Towa's boat, sending it to the lake. Celebi fires again, but luckily, Suicune rushes in to save the day! It picks up Ash and Yukinari and runs off to safety. Vicious notices Suicune, and decides he wants it too. He releases his Dark Tyranitar and, as usual, it goes on a rampage. Brock releases Onix to help out, But Onix is defeated. Suicune uses Ice Beam and Tyranitar goes down. Onix uses its last bit of strength to send Tyranitar flying into the lake. Brock returns Onix and Suicune goes after the branch monster. However, vines grapple onto Suicune, shocking it with dark energy.

Ash and Yukinari jump off Suicune to rescue Celebi. They climb the vines to an opening. They call out to Celebi, and Celebi remembers the time it was flying with Ash and Yukinari, and then stops attacking Suicune. Celebi starts to remember the moment they were at the berry tree, after Ash and Yukinari stopped it again from attacking. Vicious commands Celebi to attack once more, and it does so. As the two boys get to the top, they get Celebi to remember when they were watching a whole bunch of Butterfree at the top of a tree. Finally, Celebi comes to its senses, and the monster crumbles into the lake. With the monster out of the way, Celebi, Ash, and Yukinari float down to the edge of the lake.

They take Celebi to touch the water, but the water is too impure. Suicune tries to purify the water, but still, Celebi isn't revitalized. Ash tries to give Celebi a berry he got from the berry tree, but doesn't work. He keeps trying, and trying, but again, doesn't work. They've lost all hope. Is Celebi gone forever?

Then, the forest starts to glow a bright blue, and out of the lights come a multitude of Celebi. The other Celebi use their powers to revive Yukinari's Celebi, and it works! But, Vicious appears from the water and catches Celebi! He then flies off with his jet pack. Ash and Pikachu grab onto his leg to save Celebi. Pikachu uses a successful Thunderbolt attack. The jet pack blows up, and everyone falls. Ash tries to catch Pikachu . . . but he knows he'll fall to his death. Celebi, however, saves Ash and Pikachu with its Psychic. Vicious falls into the forest, coming upon Towa, Mika, and Diana, all three having angry faces. Towa cracks his knuckles likes he wants to fight. Mika scolds at Vicious because of his stupidity. Dozens of angry Pokemon gather around him also. Vicious tries to use Scizor and Sneasel, but he forgot that he left them behind! The String Shots of Caterpies, Weedles, and Spinaraks then trap Vicious.

Celebi comes back, and opens the time portal so Yukinari can get back home. Everyone says good-bye, but Ash isn't ready to part from a good friend yet.

Later, James and Meowth get to Jesse in a raft, and get her out of the water. And while arguing, Tyranitar jumps out of the water and smashes their raft. Without a raft, the three decide to float there.

40 years into the past - Yukinari wakes up in front of the shrine, and Celebi is nowhere to be seen. Running up to Yukinari is Diana, asking him if he's all right.

The end.

This episode guide has been written by Psythor.

Characters appearing in this episode

Ash

Brock

Jessie

James

Meowth

Ash's Pikachu

Pokémon appearing in this episode

• Pikachu belonging to Ash
• Meowth