Dr. Abner Perry and David Innes test their experimental drilling machine, the Iron Mole, when an unexpected malfunction sends them plummeting to the Earth's core. They discover a fantastical world called Pellucidar, populated by primitive human tribes and ruled by telepathic, reptilian creatures known as the Mahars. Captured by these overlords, Perry and Innes struggle to adapt to the hostile environment, building alliances with the enslaved tribes. Innes becomes particularly close to a courageous warrior named Ra and a noble maiden named Dia, who were also captured and are vital to their survival.

As they communicate with the enslaved humans and learn more about the brutal rule of the Mahars, Perry and Innes formulate a plan to revolt. Innes is driven not only by the injustices he witnesses but also by his growing affection for Dia. Utilizing scientific knowledge and their resourcefulness, Perry and Innes aim to incite an uprising that could liberate the tribes from their subjugation. Their journey becomes a perilous adventure filled with unexpected allies and formidable enemies as they press forward in their quest for freedom against overwhelming odds.