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.
Lionel Barrymore
as Andre Dakkar
Jacqueline Gadsden
as Sonia Dakkar
Lloyd Hughes
as Nikolai Roget
Montagu Love
as Falon
Montagu Love
as Mikhail
Snitz Edwards
as Anton
Gibson Gowland
as Dmitry
Dolores Brinkman
as Teresa
Karl Dane
as (uncredited)
Pauline Starke
as (uncredited)
Carl Roup
as Underwater Creature (uncredited)
Angelo Rossitto
as Underwater Creature
