Albert Werper a deserter from the Belgian army has come to Tarzan’s estate posing as a hunter. In reality he is in league with Achmet Zek an Arab slaver who wants Tarzan dead. During his visit Werper overhears Tarzan’s plan to go to Opar. It seems that Tarzan has lost his fortune in bad investments and must replenish it with the gold from the lost treasure of Opar. Werper gets word to his partner and follows Tarzan to Opar.
At Opar an earthquake strikes and Tarzan is knocked unconscious and trapped in the treasure vault. He awakens with amnesia and no memory of his civilized life. Collecting a bag of jewels he thinks of as pretty stones he comes upon the altar room of Opar. The beast men have captured Werper and are about to sacrifice him. Tarzan rescues him and still rejects the love of La the high priestess.
Werper being the sleazy rogue he is steals the bag of jewels. What follows is an adventure as Tarzan tracks Werper and must fight a vengeful La and her Oparian beastmen, Achmet Zek, Belgian troops and a renegade Abyssinian army.
The fifth novel in the series really starts to hit its stride. This book has what makes the Tarzan series exciting. Evil Europeans, traitorous Arab slavers, lost cities and dangerous beasts. This book is definitely a classic. Its one of my favorites in the series and sets the tone for what makes the series such an enjoyable read.