Repeated earthquakes are shaking Industria, and the island will soon sink beneath the sea. As its people get ready to leave, they are attacked by Lepka, a foe they thought was dead. He has been lying low underground, planning to seize Industria's solar power to run Gigant, a warplane built for mass destruction that he means to use to rule the world. Lana and Monsley see through his scheme and slip away to warn Conan and his friends, who are readying a ship to evacuate the island. Conan then sets out with Dyce and Jimsy on a dangerous mission to take Gigant down. The film is a sci-fi adventure drama that recuts the last three episodes of the television series, and it was released alongside Kaze no Tani no Nausicaä.