Old Time Radio Sci-Fi, Horror Etc...

The crew are stuck on the Moon and unable to trace what has caused the power failure. A fortnight passes, with the air temperature rising uncomfortably in the absence of air-conditioning. A UFO is seen on the televiewer and strange noises are heard. When they are left with just enough oxygen to reach home, power is suddenly restored to the ship, and the UFO is seen to have landed outside.

Mitch is inquisitive and enters the UFO, where he is temporarily possessed by an alien intelligence. Luna takes off and orbits the Moon. On the far side, the crew encounter a fleet of UFOs, which pursues them.

The UFOs accelerate Luna to an incredible speed, and the crew blacks out. On recovering, they find themselves out in deep space, with no sign of the Earth or Moon. In the distance, a planet is approaching.

The crew land Luna on the planet and discover that it shares many of Earth's characteristics – oxygen atmosphere, drinkable water, carbon-based vegetation and ice-caps at both the poles. After studying the stars one night, Jet deduces that they in fact are on Earth, but that they've travelled thousands of years through time.

Jet discovers a prehistoric stone knife near Luna, suggesting that they've travelled back in time, but there is some confusion over this when the crew discover the tracks of a great tank-like machine near their ship. A UFO, exactly like the one seen on the moon, lands nearby and a voice is heard over the radio: "Hello Luna!".

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The crew talk with 'the voice'. They learn that the strange music they've been hearing is generated by a strange, omnipresent power that 'the voice' and his people use to drive their ships. 'The voice' warns them that they are in great danger, and persuades them to enter the UFO, which takes off. Eventually it lands again, in a city of domed buildings.

The crew learn more about 'the voice' and his people – they are a peaceful, scientific race from the opposite side of the universe. The crew explore the city, and are disturbed by a close encounter with a sabre-toothed tiger. Fortunately, the creature does not attack them, but they now realize that they have travelled back through time instead of forward. They enter a domed building, walk down a long dark tunnel, and emerge in a huge underground city...

'The voice' consoles the crew, who are embarrassed by their shock, and guides them to another dome where they are given a meal and beds to sleep in. Next morning, 'the voice' tells the crew about the Earth's native 'forest creatures', destructive and hostile animals, and promises to help the crew get back to their own time. While preparing Luna for take-off, the crew are horrified to realize that the 'forest creatures' are, in fact, prehistoric humans.

'The voice' is not pleased to learn that the crew are descended from the 'forest creatures', but in the end agrees to help them as arranged. Luna takes off and is accelerated by the UFOs; the crew blacks out. They start to ponder on the nature of time, and become concerned about their shortage of fuel, and whether they will remember their adventures when they reach their own time.

The crew successfully return to the Moon in 1965, but with no memory of their adventure on prehistoric Earth. However, their rations have been replaced by water and an unknown bread-like substance, Doc's diary contains a detailed account, and there's a prehistoric stone knife on board Luna...