In a dystopian near-future Japan, an influenza virus spreads throughout the canine population, with a risk of crossing to humans. The 6-term authoritarian mayor of Megasaki City, Kenji Kobayashi, signs a decree banishing all dogs to Trash Island, despite a scientist named Professor Watanabe insisting he is close to finding a cure for the dog flu. The first dog to be exiled is Spots, a white and black-speckled pink-nosed dog who served as the bodyguard of Atari Kobayashi, the orphaned nephew and ward of the mayor. Six months later, Atari steals a plane and flies to Trash Island to search for Spots. After crash-landing, Atari is rescued by a pack of dogs led by a seemingly black dog named Chief, who is a former stray. The pack decides to help Atari locate Spots, although Chief refuses to join because of his inability to fraternize with humans. Together, they fend off a rescue team accompanied by a robot dog that Kobayashi sent to retrieve Atari..