In a forest in the Johto region, a young Pokémon Trainer named Sammy crosses paths with a warning from a woman named Towa — Mami Koyama — about the mysterious and mighty Voice of the Forest. The legend centers on Celebi, a Mythical Pokémon capable of bending time across past, present, and future. Celebi is pursued by a relentless Pokémon Hunter and sustains injuries in the chase. Sammy steps in to shield Celebi from harm, and in a flash of power, the mythical creature uses its abilities to leap forward in time, carrying Sammy along with it.
Forty years slip by, and the aging hunter confronts a new, cruel force: the Iron Masked Marauder, a ruthless operative of Team Rocket who schemes to bend Celebi’s powers to his own dark ends. The Marauder wields Dark Balls, a sinister type of Pokéball that can seize Pokémon already bound to their Trainers, twist their nature, and amplify their strength to terrifying levels. He proves his threat by capturing the hunter’s Tyranitar and ordering it to unleash a devastating Hyper Beam to wreck what remains of the hunter’s possessions.
Across time, Ash Ketchum, Misty, and Brock arrive in the vicinity of Arborville and witness the legendary Suicune along a riverbank. In conversation with Professor Oak, they learn he once met Suicune years earlier, though he cannot fully explain the tale in that moment. A local guide named Mr. White leads them toward the forest, where they encounter the elderly Towa and her granddaughter Diana, who warn them about the Voice of the Forest. Celebi and Sammy emerge from the past, though Celebi hides itself while Sammy gradually comes to terms with his displacement through time. The group—Ash, Sammy, Misty, and Brock—move to help the wounded Celebi, bringing it toward the fabled Lake of Life, where its healing waters may aid.
That night, a bond forms between Ash and Sammy as they hope for a future where the younger trainer might reunite with his friends in his own era. The next day, the Marauder closes in, deploying a Dark Ball to capture Celebi and envelop it in a colossal, forest-made armor that amplifies its power. In the ensuing struggle, Jessie is captured, and the Marauder reveals a broader ambition: to overthrow Giovanni and seize control of the world for himself. Ash, his companions, and Suicune fight to free Celebi from the Marauder’s influence.
In a tense moment, Ash, Sammy, and Pikachu manage to breach Celebi’s armor and persuade the time-traveling Pokémon to resist the Marauder’s control. Celebi regains its memories and breaks free from the Dark Ball’s hold, but tragedy strikes as Celebi dies in Sammy’s arms by the lakeside. Suicune’s purification magic touches the lake, yet it cannot revive Celebi—until the Voice of the Forest reveals itself as Celebi across time and conjures a miraculous resurrection.
Just as all hope seems lost, the Marauder reappears and abducts Celebi with a jetpack, escaping into the skies. Ash and Pikachu intervene, rescuing Celebi, while the Marauder crashes into the forest and is confronted by Towa, Diana, White, and a gathering of furious wild Pokémon. With Celebi returned to safety, Sammy is sent back to his own era, promising that he will meet Ash again in the future. Professor Oak’s conversation with Ash leaves them puzzled about how Oak knew Sammy’s name, a mystery that lingers as Oak studies a sketchbook in his lab.
In a twist of fate, Tracey Sketchit discovers Oak’s sketchbook and places it on a shelf for safekeeping, preserving the evidence of the time-tangled friendship. And even as the lake glitters with the aftermath of their adventures, Jessie reunites with James and Meowth on the lake’s edge, hinting at the ongoing, larger-than-life dynamics of the Pokémon world.
