When an unidentified "monster" threatens international shipping, French oceanographer Pierre Aronnax and his unflappable assistant Conseil join an expedition organized by the US Navy to hunt down and destroy the menace. After months of fruitless searching, they finally grapple with their quarry, but Aronnax, Conseil, and the brash Canadian harpooner Ned Land are thrown overboard in the attack, only to find that the "monster" is actually a futuristic submarine, the Nautilus, commanded by a shadowy, mystical, preternaturally imposing man who calls himself Captain Nemo.