After Lana is kidnapped by the two soldiers from Industria, Conan fails to rescue her. Conan's grandfather dies from his injuries. After burying his grandfather, Conan builds a boat and sets off to rescue Lana.

Conan arrives at an island where a wild boy, Jimsy, lives. After an initial fight, Conan develops a good friendship with Jimsy. The Baracuda comes to the same island, getting the inhabitants to salvage for plastic. After Conan finds out the Barracuda is from Industria, he and Jimsy plan to stow away aboard the ship.

Jimsy and Conan sneak onto the ship, but Jimsy gets drunk and alerts the captain of their presence. After the boys are caught, Captain Dice lets Conan and Jimsy stay on the ship if they will take punishment. Jimsy passes out and Conan takes both their beatings. They work on the ship doing random jobs. Finally, the ship sets sail for Industria.

After the Barracuda arrives in Industria, Conan is thrown in the brig after he assaults Monsley who was visiting the ship. Lepka, the self-serving chief administrator of Industria's High Committee, tries to threaten Lana into telling him where her grandfather is. Monsley decides to take Conan in for "re-education". When the soldiers come to take him, Conan escapes and, after a rough flight through the bowels of Industria, eventually finds Lana.

While making their escape, Conan and Lana come upon a plane from the last war that Lepka wants to power with Dr. Lao's solar energy process for his plans of world conquest. They are captured, and Lepka threatens to hurt Conan if Lana doesn't tell him where her grandfather is, but she refuses. Upon witnessing Lepka's viciousness, Dyce decides to help Lana. Dyce and his crew kidnap Lana and make their escape on the Barracuda.

Dyce escapes in the fog. Lepka gets permission to use the gunboat and Falco to pursue Dyce. Conan escapes from jail and sneaks onto the Falco. Jimsy informs Lana that he is a companion of Conan. Dyce meets with Lana and when she gets angry that he left Conan he opens the window and threatens to throw her out. The Falco sees the light and follows the Barracuda. Conan escapes and attempts to board the Barracuda.

Lana escapes and uses a lifeboat to save Conan. The gunboat boards the Barracuda and captures Dyce and his crew. Lana and Conan escape on the lifeboat. While trying to make it to the shore, the gunboat blows up the lifeboat, but Conan and Lana survive and make it to the nearby island, where they discover an old battlefield littered with tanks. Lana hears her grandfather by telepathy, and Conan and Lana set out to cross the desert.

After crossing the desert, Lana and Conan are discovered by a man named Patch, who works at an Industrian salvage platform where a passenger ship is about to be uplifted from the seabed. After proving his diving skills to Patch, Conan and Lana are set to work. Terit, an ambitious worker on the platform who longs to be elevated to a higher grade of citizenship in Industria, tries to identify them. He sneaks onto the Falco, which stopped by, and informs Monsley that Conan and Lana are there.

Terit returns to Industria and is given a radio to inform Lepka when Lana meets her grandfather. However, an earthquake hits the desert island; Patch goes down and gets trapped beneath the ship, and Conan rescues him. When Patch is revealed to be Dr. Lao, Terit informs Industria of Dr. Lao's presence; but another tremor causes the beach near the salvaging platform to sink into the ocean, and the platform begins to float out to sea. Knowing that Industria will send forces to capture them, Lao, Conan, and Lana escape in a small lifeboat.