Earth’s International Space Order prepares for its first manned landing on the Moon, with the goal of claiming it as “international territory”. The crew of Lunar Eagle 1 comprises 12 people from around the world, 10 men and two women, all scientists with different specialties, accompanied by a small menagerie, including two cats. The spaceship is commanded by American John Anderson (Ken Clark).
Historical and international tensions flare up during the flight. Feodor Orloff (Tom Conway), a Russian, struts about, annoyingly claiming that all scientific advancements were invented by the Soviets. Israeli David Ruskin (Richard Weber) warns Feodor that the USSR would be unwise to attempt to dominate Israel, as it has his native Poland. David admires fellow astronaut Erich Heinrich (John Wengraf), unaware that Erich’s father was the Nazi responsible for murdering David’s family during the Holocaust.
After a dangerous 27-hour flight, Lunar Eagle 1 lands and the crew begin their exploration of the Moon. Sigrid Bomark (Anna-Lisa) and Selim Hamid (Muzaffer Tema) find an air-filled cave and after shedding their space helmets, they kiss passionately. As they walk hand-in-hand deeper into the cave, its opening is suddenly sealed by impenetrable ice.
The others discover gold and minerals, but when they fire a mortar into a rock formation, liquid begins bubbling out. An excited Feodor rushes over and sticks his hands into the flow, and he is badly burned. On the way back to their spaceship, a crew member sinks to his death in lunar quicksand. John tries unsuccessfully to save him and is almost pulled under.
Inside Lunar Eagle 1, a machine begins printing out hieroglyphics. Surprisingly, Hideko Murata (Michi Kobi) can read them. It is a message from “The Great Coordinator of the Moon”, who orders the crew to leave at once. The message also states that the emotionless Moon-beings live underground and fear that the Earthlings will “contaminate our perfect form of harmony”. Sigrid and Salim are being studied because the Moon-beings are unfamiliar with “love”. They and “all your kind” will be destroyed “if love turns to evil”. The Moon-beings also demand that the expedition’s cats, brought as an experiment to see if they could procreate on the Moon, be left behind. They find the felines as interesting as people.
Erich has a heart attack during Lunar Eagle 1’s blast off. As he babbles on half-conscious, David learns that Erich’s father was the Nazi who killed David’s family. However, when David learns that Erich has disowned his family and devoted his life to trying to make amends for his father’s crimes, they become friends.
Near Earth, the crew witnesses “the big freeze”, a gigantic freezing cloud controlled from the Moon, which encases all of Canada, the U.S., and Mexico in thick ice.
John decides to drop “atomic bomblets” into the volcano Popocatepetl in order to trigger a huge eruption to thaw out North America. Etienne Martel (Roger Til) sabotages the bomblets, revealing himself to be a French communist. He assumes that Feodor would also want to keep America frozen in order to advance international communism’s quest for world domination. Feodor doesn’t. He and Etienne fight, Feodor calls to John for help, and when Etienne unfairly pulls out a knife, John knocks the weapon out of his hand, while knocking him down. Feodor repairs the bomblets.
Erich and David fly a suicide mission to drop the bomblets from their spaceship’s smaller space taxi. Popocatepetl erupts and North America begins to thaw. Another message from the Moon says that the Moon-beings now realize that Earthlings are honorable and peaceful, and that the North Americans were put into suspended animation before the big freeze, so no-one has been harmed. Moreover, Earthlings will be welcomed to the Moon whenever they return.
Following the great thaw, Lunar Eagle 1’s triumphant crew prepare to land.