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.

Railroad builders, preparing to tunnel through the mountain where Snagglepuss resides, encounter so much trouble from the firmly entrenched lion that they ask big game hunter Major Minor for assistance.