In Siberia, an archeological expedition searching for prehistoric fossils discover a large prehistoric monster, perfectly preserved in a state of suspended animation in the ice.

Two escaped convicts are found hiding in a rocket ship built by a renegade inventor, who forces them to become the crew for a trip to the Moon. Also on board, as inadvertent stowaways, are his assistant and his secretary; and none of them are aware that the inventor is actually a Lunarian explorer sent to Earth by the dying Lunar civilization.