Tarzan discovers Ibn Jad’s Arab expedition moving through the African wilderness in search of ivory and legendary treasure, while the Americans James Blake and Stimbol are drawn by a series of dangers into the same mysterious mountain country. Beyond a great cross, Blake enters the hidden realm of Nimmr, whose inhabitants still preserve the customs and chivalric traditions of the Crusades, and he falls for Princess Guinalda only to become involved in a deadly contest with the knight Sir Malud. Meanwhile, Tarzan’s conflict with the treasure-seeking Arabs intensifies as Ibn Jad’s party approaches the forbidden valley from which no outsider is believed ever to have returned, bringing the separate adventures toward the same hidden world.
