When tales of ships disappearing and possibly being destroyed by a creature from the depths of the sea emerge, the government sends a ship to investigate. The monster turns out to be real and it sinks the ship sent to investigate it. The only survivors are Ned Land (Kurt Douglas), Professor Pierre Arronax (Paul Lulas) and Conseil (Peter Lorre) who find themselves in the company of Captain Nemo (James Mason) who seems to move back and forth between reason and insanity. Captain Nemo has plans to destroy the world and has the technology help him achieve his goals in his ship, the Nautilus. The three "captives" are invited along as the ship explores the depths of the sea. Ned seems to be the only one desiring to escape as both Conseil and Prof. Arronax are happy to be part of the exploration. Ned finally is able to get a note in a bottle to the Navy. Can they stop Captain Nemo before he discovers the secrets he needs to destroy the world?