A team of explorers sets on a voyage to the earth's core, following an earlier attempt years before. Their ship, ''Avenger'', enters the lava chamber of an active volcano and uses an energy ray called a "sonic blaster" to blast through the flow. They enter in a subterranean world over 100 kilometers below the Earth's surface. The place is filled with many strange creatures. As they explore deeper into the underground caverns they encounter a yeti which the crew named Dallas that serves as their guide. Meanwhile, an unknown malevolent entity is attempting to recover the missing pieces of an Atlantis artifact known as the "book of knowledge" one of which a crew member of the Avenger brought with him, that will supposedly give massive powers to whoever possesses it.