Description
Three men - Dr. Ken Tashiro, Dr. Jules Masson, and journalist Perry Lawton - are trapped in a bathysphere due to seismic activity. They are rescued by the crew of the supersubmarine Alpha, captained by Craig McKenzie (Cotten), who they learn is over 200 years old (and that the Alpha was launched in the early 19th century). McKenzie takes them to Latitude Zero to heal Dr. Masson's injuries. Along the way, they are attacked by a rival supersubmarine, the Black Shark, captained by Kuroi (Hikaru Kuroki), who works for a rival of McKenzie's, Dr. Malic (Romero). Using super-technology, McKenzie gives the Black Shark the slip.
The crew of the Alpha soon return to Latitude Zero, a super-advanced utopia hidden fifteen miles below sea level at the intersection of the Equator and the International Date Line populated by people from all over the world reported missing in accidents at sea. It has existed since the 19th century, as none of its inhabitants age or die, and greed and political divisions plaguing the surface world are unknown here. It also surreptitiously assists mankind's technological and cultural advancement. Malic, however, wishes to destroy Latitude Zero using superweapons and artificially grafted monstrosities like giant rats and anthropomorphic bats. He kidnaps a Japanese physicist allied with McKenzie, Dr. Okada, and his daughter Tsuruko, and forces Okada to assist him in his schemes. Moreover, after a cruel experiment grafting the wings of an eagle to a lion, he removes Kuroi's brain and places it in the creature as punishment for her failures.
Upon receiving an emergency signal from Okada, McKenzie organizes a rescue expedition, and Tashiro, Masson and Lawton, as well as Latitude Zero physician Dr. Anne Barton (Haynes) and Kōbo (Ōmae), volunteer to help. Equipped with James Bond-style devices and rendered resistant to physical harm by a special bath, they infiltrate Malic's island base, Blood Rock, fight their way to the enemy control center, and rescue the Okadas. As the team escapes, Malic enters the Black Shark and fires an onboard laser at them. Just then however, Kuroi turns against Malic and attacks the laser, causing the weapon to fire at the island's cliffs, which collapse on the submarine and destroy it along with everyone aboard.
Of all the visitors to Latitude Zero, only Lawton (Jaeckel) wishes to return home. He is picked up by a US Navy vessel, where he meets Commander Glenn McKenzie (also Cotten) and Lt. Hastings (also Romero). Startled by these similarities, Lawton additionally discovers that all his knowledge of Latitude Zero's existence was either ruined or taken. Just as he is about to resign himself to the idea that his adventure never occurred, the ship receives a message stating that a cache of diamonds has been deposited in his name in a safe deposit box in New York City, and the ship is ordered to change course to Latitude Zero.
