Kenneth Robeson 
The Phantom City [EPUB ebook] 

Arabian thieves led by the diabolically clever Molallet set one fiendish trap after another for Doc Savage and his mighty five. Only "Doc, " with his superhuman mental and physical powers, could have withstood this incredible ordeal of endurance which led from the cavern of the crying rock through the pitiless desert of Rub' Al Khali and its Phantom City to a fight to the death against the last of a savage prehistoric race of white-haired beasts.