Tai wonders if his sister Kari is the eighth child. Tai's cat Miko knocks a digidevice over the balcony and goes after it. Meanwhile a new Digimon called Raremon begins to terrorize some people by the bay. Izzy checks his computer and Gennai tells him that the other kids are asleep in their houses. Izzy and Tentomon go after Raremon. Izzy's digivice indicates that the eighth child is nearby. He continues to track him, while Tentomon digivolves to Kabuterimon and defeats Raremon. Miko loses the digivice to various animals, until a crow ends up with it.
The city is rocked by the recent wave of monster sightings and bizarre weather patterns. Tai and the others search the Shibaura section of the city, hoping to find the eighth child before Myotismon does. One of his minions, Gatomon, happens to meet Kari in the park and is convinced that she's the eighth child. Meanwhile, Mimi and Sora stumble into the monstrous, flame-belching SkullMeramon. Agumon has to digivolve into Greymon and then MetalGreymon before finally giving the monster a fiery farewell.
Matt is taking little brother T.K. home on the train when T.K. and Patamon get into a fight. Patamon takes off and Matt, T.K. and Gabumon head out looking for him, but instead run into two of Myotismon's henchmen, Pumpkinmon and Gotsumon. When Myotismon shows up, the two "henchmen" don't have the hearts to attack the kids, so Myotismon blasts them to smithereens. It turns out they've just been zapped back to the Digital World, but the kids think they're gone for good. T.K. gets so upset that Patamon digivolves into Angemon! Soon Myotismon is running away, and the kids return to their search for the eighth chosen child.
Gatomon has been staking out Kari from a rooftop, but still can't be sure if she's the chosen child or not. Gatomon can't remember anything that happened before she met Myotismon. Wizardmon finds the digivice, but doesn't want Myotismon to get his hands on it, so he tricks Demidevimon into thinking he's still looking for clues. Wizardmon brings the digivice to Gatomon and helps her remember that all her life, she's been waiting for Kari. She approaches Kari and Agumon attacks, thinking she's hurting Kari. Gatomon protects Kari, proving that she's her Digimon and that Kari is the eighth child. Myotismon is not convinced that Gatomon is the chosen one, but thinks he can find the true eighth digidestined capturing Gatomon and using her as bait.
With his fogbank barrier isolating the Odaiba district of the city, Myotismon searches for the eighth child, using Phantomon and his minions to round up the district's inhabitants, including Sora, Mimi, Tai and Matt. Joe and T.K. desperately try to find a way into Odaibo. Meanwhile, Sora blasts a self-help tape at Phantomon's spooks, neutralizing them. But this only works temporarily and, with the arrival of the towering Dark Tyrannomon, things look bleak until Togemon transforms into Lillymon, and tames the beast. Sora is reunited with her estranged mother as Lillymon takes on the evil Myotismon himself.
Tai goes to rescue his parents and the others being held prisoner by Myotismon. Gennai tells Izzy how to create a Digital Barrier to protect his family from Bakemon. While trying to get into Odaiba to help, Joe and T.K. are attacked by MegaSeadramon. After Ikkakumon digivolves into Zudomon and defeats the beast, they find Wizardmon in the water with the crest of the eighth child. Phantomon follows Sora to Matt and Kari's hideout where he summons two Digimon to destroy the children. Feeling responsible, Kari confesses that she's the eighth child and offers to surrender to Phantomon if he will stop hurting her friends. The villain agrees and carries her off.
Kari has just surrendered to Myotismon. Wizardmon tells the others they have to return Kari's tag and crest to defeat Myotismon. Myotismon tricks Gatomon into revealing that Kari is the eighth child. Myotismon is about to destroy them when the kids and Digimon arrive. Despite the Digimon fully digivolving, they still lack the power to defeat Myotismon. Myotismon unleashes a deathblow to Kari and Gatomon, but Wizardmon jumps in front and dies from the blast. Tai gets the Digivice back to Kari, which helps Gatomon Digivolve to Angewomon. All the Digimon divert their power to Angewomon, who strikes down Myotismon with her celestial arrow. It seems that Myotismon is defeated, but the kids find it strange that the fog has still not cleared.
Gennai uncovers a cryptic prophecy that could lead to the salvation of the Real and Digiworlds, if Izzy and the others can decipher it. Elements of the prophecy begin to come true: bats appear in the sky, the captured residents of Odaiba call out Myotismon's name in a trance, Gatomon digivolves into Angewomon, and Myotismon rises again, revealing himself in his "true" form, a towering, energy-devouring monster. In an attempt to bring about the last part of the prophecy, Angemon and Angewomon shoot arrows of light at Tai and Matt, causing Agumon and Gabumon to "warp-digivolve" into their ultimate selves: War Greymon and MetalGarurumon.
Agumon and Gabumon warp-digivolve into WarGreymon and MetalGarurumon. Incredibly, their combined power is still not enough to defeat VenomMyotismon. Not until all the Digimon combine their attacks as one do their crests begin to glow and VenomMyotismon disintegrates. The kids look up to see the sky beginning to break apart and a huge landmass looming towards them. Terrible things begin to happen as Izzy deduces that the continent is in fact the Digital World! The kids and their Digimon realize that they must return and fix the problems there in order to save the Real World. Sadly, they say goodbye to parents and rise bravely into the sky.
The digidestined and their companion Digimon find themselves hurled back to the Digital World after defeating Myostismon. Chuumon tells them that the four Dark Masters have relocated the Digital World to Spiral Mountain and are planning to take it over. MetalSeadramon challenges them. The Digimon digivolve to champions, but are unable to defeat him, as he is an ultimate Digimon. They meet the second Dark Master, Machinedramon and can't defeat him, either. The third Dark Master, Puppetmon, controls them with strings and drops them off to meet the fourth Dark Master, Piedmon. Piximon comes to the rescue and the digidestined escape.