As the world progresses into the industrial age, a professor studying the "nature of pure matter" is spirited away by a would-be dictator and connived into building a super-bomb, as a young reporter and a girl rescued from the sea attempt to warn him of their mutual kidnapper's intentions to dominate the world with a new and more-deadly-yet weapon.

On a volcanic island near the Kingdom of Hetvia rules Count Dakkar, a benevolent leader and scientist who has eliminated class distinction among the island's inhabitants. Dakkar, his sister Sonia and her fiance, engineer Nicolai Roget have designed a submarine which Roget pilots on its initial voyage just before the island is overrun by Baron Falon, despotic ruler of Hetvia. Falon sets out after Roget in a second submarine and the two craft, diving to the ocean's floor, discover a strange land populated by dragons, giant squid and an eerie undiscovered humanoid race.