In this 1921 adventure novel from the original Tarzan series, the ape man discovers a lost world of dinosaurs where his beloved Jane is being held captive. When World War I broke out across the African colonies, an attack on Tarzan's estate led him to believe his wife Jane had been killed by Imperial German soldiers. But after a months-long rampage of vengeance, he learns she is in fact still alive-he only need find her. Before long, his search will take him from the modern threats of tanks and war planes into a land of prehistoric dangers. In the hidden valley of Pal-ul-don, dinosaurs continue to thrive, and the warrior tribes of the Ho-don and Waz-don-who appear to be human apart from their tails-are locked in bitter conflict. Somewhere in Pal-ul-don, Jane is being held captive. But to save her, Tarzan must survive a gauntlet of deadly enemies with a display of strength and skill that will earn him the name Tarzan the Terrible.