The words "Thirty years ago, Professor Manfeldt, a famous expert," precedes a shot of young Manfeldt teaching a class. Manfeldt lectures other scientists with his belief that there are gold deposits on the moon. He says that someday space ships will be built to go there and collect the gold. The other scientists make fun of him. The next caption says "Today, Professor Manfeldt, an old man." The scene opens with Manfeldt old and crazy looking. His belief about the moon is still as strong as ever, and he keeps experimenting. Manfeldt has found someone who will finance his space ship, Wolf Helius. Helius tells Manfeldt that he has found a recently engaged couple who are very interested in his work, Hans Windegger, an engineer, and Frieda Velten, a student of astronomy. Turner, the head of the group of financiers, shows everyone designs, charts, picutres of the darkside of the moon, and a short film shown through the lenses of an unmanned rocket. All the businessmen want the gold on the moon since they already have control of the gold on earth.
Helius tells Manfeldt that he has to let Turner and his group in on the project because Helius does not have the money to finance it on his own. At least the men will make Manfeldt's dream come true. Helius recieves a worn copy of Manfeldt's notes on the moon. After be given the notes, Helius precedes to tear up a note from Hans and Frieda about their engagement. Hans does not like Turner's group, nor do they like him. Yet, somehow, Helius arranges it so Turner and company can come along on the trip.
The night of the space ships launch is full of crowds of people, all trying to get a view of the spaceship. Newsmen take a close look at the ship inside and out, as they write down every detail. The ship takes off and all are struck unconscious by the rocket's buffeting. Helius wakes up first and walks over to check on Frieda. Hans wakes up and gets jealous when he sees them together. Helius is ashamed of his feelings for Frieda and walks away reluctantly.
Frieda goes to the store room and finds a little boy, Gustav, who stowed away on the ship. Meanwhile, Turner wakes up looking rather sinister as he putters around the ship and meddles with the boy's bag. Gustav and Frieda have fun looking at science fiction magazines. Meanwhile, Manfeldt keeps his eyes on his telescope and the stars. Everyone straps themselves into their chairs as the moon's craters come into view.
Hans gets nervous and does not want to land. He says that it was Helius and Helius' ambition that had gotten them into all this. Helius is the one to calm Hans down as the surface of the moon rushes up to meet the landing craft. The ship crashes in a huge explosion deep into the moon. The equipment is all damaged, and Hans says that "the only thing we will find on the moon is death."
The water casks were damaged on impact. Manfeldt uses his divining rod to look for more water while the rest of the group is still in the ship. When the others finally emerge from the craft, Turner volunteers to go find both Manfeldt and water. Frieda bandages Helius' hand that was hurt during the landing. The love between them is becoming more obvious. Gustav and Hans start digging out the ship, in hopes of getting back home.
After his hand is taken care of, Helius takes Gustav in search of Manfeldt. Meanwhile, Manfeldt is walking over hot springs with Turner behind him. Manfeldt is unaware of Turner and walks into a cave. He finds big gold rocks in the cave, and starts to hug them. Manfeldt turns around to find Turner following him. He loses his balance on the cliff and falls to his death. Turner ignores the body and goes straight for the gold. Gustav and Helius finally get to the cave to find Manfeldt dead at the bottom of the cliff.
Turner comes back to the ship and incapacitates Hans, tying his hands behind his back. Turner creeps up behind Frieda, who is on the ship developing film. She sees him and tries to escape. Helius and Gustav return to find Hans, who has freed himself, fighting with Turner. Hans deals Turner a mortal wound, and Turner shoots at the oxygen tanks to prevent them from leaving the moon. Helius and Hans examine the tanks and find that only one person has to stay behind. Everyone draws straws and Hans cries out in grief when he loses.
Helius wants to be the one that stays behind. So, he drugs Frieda and Hans. He then shows Gustav how to lift off and watches on the surface as the boy flys the ship toward earth. Helius begins to weep in his loneliness, and then starts in surprise as Freida walks out from behind the supplies. They hug each other in love and happiness. The caption says that this act is the greatest proof of love there is.