When a message is found from lost explorer Bowen Tyler (Doug McClure) detailing a prehistoric world at the center of the Arctic Circle, fellow adventurer Ben McBride (Patrick Wayne) gets a newspaper to sponsor a search. The search takes McBride to the tropical oasis Tyler wrote about, the isle of Caprona, where he meets a feisty cavegirl named Ajor (Dana Gillespie). She explains that Tyler has been kidnapped by a warrior tribe called the Naga. Now it's up to McBride to rescue him.