LATITUDE ZERO

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, 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 Kuroiga, who works for a rival of McKenzie's, Dr. Malic. 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 a condor to a lion, he removes Kuroiga'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. Tashiro, Masson and Lawton, Latitude Zero physician Dr. Anne Barton, and Kōbo 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, but Kuroiga turns against Malic and attacks the laser. The weapon collapses the island's cliffs onto the submarine, destroying it and killing everyone aboard.

Of all the visitors to Latitude Zero, only Lawton wishes to return home. He is picked up by a US Navy vessel and discovers that all his knowledge of Latitude Zero's existence has disappeared. 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.

After a final confrontation involving mutant creatures and a rescue mission on Malic's island base, the heroes escape as Malic's submarine is destroyed, and Lawton later finds evidence that his adventure at Latitude Zero may not have been a dream after all.

The ending wraps the science-fantasy adventure with a blend of resolution and ambiguity. Malic’s defeat comes from internal betrayal, capping the film’s motif of unpredictable alliances, while Lawton’s ambiguous return to the surface and the hint of Latitude Zero’s ongoing influence give the story a mythic, liminal quality. The film leaves open whether the utopian undersea world is fantasy or a hidden reality, fitting its blend of pulp spectacle and philosophical what-ifs.