An operation to rescue Bowen J. Tyler from the hidden island of Caprona is launched, led by Tom Billings, a friend of the Tyler family. Billings crashes an aeroplane in the interior of the island and is forced to attempt to trek back to the rescue crew. Luckily, he rescues a beautiful native maiden from certain death and is able to learn much about the odd form evolution takes on this mysterious island while fighting a variety of prehistoric animals and savages.
