Jean, Nadia, Marie, and King are taken aboard the Nautilus with their new enemies-turned allies, Grandis, Sanson, and Hanson. Technophiles Jean and Hanson are thrilled to be aboard the Nautilus. Grandis becomes dangerously smitten with Captain Nemo, much to Sanson's consternation. Nadia, meanwhile, is very suspicious about the submarine and its crew, particularly Nemo, who reacts with surprise upon seeing her for the first time....

Marie and Nadia become sick from a dangerously fatal tropical fever. To save them from death, Nemo charts course for an underground reef, where he takes Jean, Sanson, and Hanson on a quest to find the cure. Coming back, however, they have to deal with a territorial, eel-like Dinicthys....

Captain Nemo's vessel falls into yet another deadly trap set by Gargoyle--one which involves the Garfish and a surprise attack from American battleships. The subsequent damage costs the lives of several sailors--including a friendly young engineer named Ensign Fait. Jean, who had become friends with Fait, is horrified and devastated to witness someone being killed by the technology he had so strongly idealized with.