Seven kids (Tai, Matt, Sora, Izzy, Mimi, Joe, and T.K.)at summer camp see some gadgets fall out of the sky, one for each of them. They are transported to another world, where they meet a group of creatures called Digimon (digital monsters). Each kid appears to have his or her own Digimon companion. The seven Digimon transform into larger digital monsters and fight as a team to defend the kids from Kuwagomon, a giant red beetle Digimon.
The kids are knocked off a cliff while running to escape from Kuwagamon. Gomamon has the fish in the river far below break their fall. On a beach near the river, the kids find some phone booths, but the phones inside say weird things. Just when they are about to eat lunch they are attacked by Shellmon. Agumon digivolves to Greymon and defeats Shellmon to save Tai.
The kids and their Digimon run into a mad Monochromon, who is fighting with another Monochromon over territory. The kids get away and find a cable car. They decide to sleep in the cable car and have one person keep watch outside. The bus is parked on top of Seadramon. Tai has first watch. A spark from the fire hits Seadramon's tail. The Digimon fight Seadramon. Gabumon digivolves to Garurumon and defeats Seadramon to save Matt.
The kids follow telephone lines to the village of Yokomon at the foot of Mt. Miharashi, a volcano guarded by Meramon. When Meramon is hit by a flying Black Gear, he becomes violent and attacks the village. The Digimon try to stop him, but they can't win against his fireballs. Biyomon digivolves to the Birdramon to save Sora. The Black Gear comes out of Meramon, bringing him under control.
The kids find a weird factory that makes useless machinery but also produces power. They find Andromon trapped in the factory, and he attacks them when they free him. Agumon and Gabumon digivolve to fight Andromon, but they lose. Tentomon digivolves to Kabuterimon and attacks Andromon's injured leg. A Black Gear comes out of his leg. Andromon shows the kids to a tunnel that leads out of the factory.
While traveling in the sewer, the kids are attacked by some Numemon. They escape, but they end up in Toy Town, where they are captured by a giant Teddy Bear Digimon, Monzaemon. The Numemon come to their rescue, and when Palmon digivolves to Togemon, they defeat Monzaemon, who had been controlled by one of the Black Gears.
The kids try to decide whether they should climb a mountain to get a view of the island. While they argue, Joe decides to climb it by himself. Gomamon follows him, and they are attacked by Unimon, who has a Black Gear inside him. Sora, Tai and Birdramon show up to help them, but when Birdramon is knocked out, Gomamon digivolves to Ikkakumon and destroys the Black Gear. Unimon flies away, and the kids climb to the top of the mountain and see that there are no other islands in sight.
Leomon, a Good Digimon, is has been made a slave to Devimon, the ruler of the Bad Digimon. Devimon orders Leomon and Ogremon, a Bad Digimon, to attack the "DigiDestined"-the kids. The kids and their Digimon fight long enough to escape and hide in a luxury hotel, but the hotel turns out to be a trick of Devimon's, and the tired group is again attacked. The kids are saved when Tai's Digivice turns Leomon back to his old self. Leomon fights Ogremon while the kids escape.
Tai and Agumon are stuck on a frozen island. They meet Frigimon, who has a Black Gear inside him. When Agumon and Tai get rid of the Black Gear, Frigimon helps them to another frozen island, where they find Matt and Gabumon. As Matt and Tai try to decide their next move, they are attacked by another Digimon with a Black Gear, Mojamon. Their Digimon digivolve and destroy the Black Gear. With the Black Gears destroyed, the group notices that the island is drifting back the way it came, toward Infinity Mountain.
Mimi and Palmon meet Sukamon and Chumon, two Digimon who share the same tiny brain. They want to kiss Mimi. Mimi and Palmon find Izzy and Tentomon when they run away from the two Digimon. Izzy tries to decipher the hieroglyphs in some jungle ruins. Mimi gets angry and wanders off. Tentomon follows. They are attacked by Centarumon, a Digimon with a Black Gear inside him. Izzy and Palmon arrive and destroy the Black Gear with their gadgets. Centarumon tells them that their Digivices resemble legendary mystical weapons against evil. Leomon arrives to attack the kids, but they escape with Centarumon's help.