In a distant Japan from a distant future, a terrible virus affects all the dogs in the country. Despite the fact that Watanabe scientist is near to finding a cure, Megasaki’s mighty mayor, Kenji Kobayashi, signs a decree by which all dogs are expelled to the Garbage Island. The first dog sent to exile is Spots, the one belonging to Atari Kobayashi, the mayor’s orphan nephew. Six months later, Atari steals a plane and goes to Garbage Island to find Spots.
After a tough landing, he is taken over by a group of dogs driven by a black dog called Chief. They decide to help Atari find the Spots, although Chief, a former stray dog, is hesitant to fraternize with people. They manage to avoid a rescue team that was sent there by the mayor to recover Atari. At the insistence of a purebred female called Nutmeg, the Chief decides to accompany them in their search.
They then seek advice from two wise dogs, Jupiter and Oracle, who warn them that there are cannibal dogs in the island’s most isolated part. Professor Watanabe finds a cure for the virus, but is poisoned by Kobayashi. An American student in exchange for experience, Tracy Walker, suspects a conspiracy and starts investigating on their own. She nods Watanabe’s former colleague, Yoko Ono, who confirms Tracy’s suspicions and gives him the last dose of the cure.