Adventurers are sent to collect specimens of flora grown by Tibetan wild men, but the specimens are protected by high priests who have placed a curse on anyone who picks their flowers.
A scientist has been experimenting on animals using radioactive isotopes, which cause a sheep to grow gold wool, spiders to spin webs made of silver, and caterpillars to weave indestructible cocoons. And that's before they increased in size...
While investigating reports of strange creatures, Mark and Elsa discover a crack in a mountainside that leads to a hidden valley. In the valley they find creatures that appear to have come from underground. Elsa, overpowered by fumes from the plant life, finds she can communicate with the creatures, and determines that together they can take over the earth.