Shipwreck survivors found on the presumably uninhabited Infant Island leads to a scientific expedition that discovers a surviving native population along with the Shobijin, tiny twin fairy priestesses of the island's mythical deity called Mothra. After the fairies are kidnapped by an exploitative businessman named Clark Nelson, Mothra sets out to rescue them.

A librarian is subject to a scientific experiment which goes wrong and transforms him into 'The Human Vapour'. He uses his new ability to rob banks to fund the career of his girlfriend, a beautiful dancer. The Human Vapour is ruthless in his quest for money and kills anyone who stands in his way, especially police. He soon becomes Tokyo's most wanted criminal. Can he be stopped before he kills again?

When a rare species of butterfly is found in a mysterious valley in Japan, a pair of entomologists go to investigate and find more. They discover Varan, a giant monster, who decides to leave the valley and head straight for Tokyo.

Nuclear tests create a radioactive man who can turn people into slime.