Cruel slave traders have invaded the jungle domain of Tarzan of the Apes. Now they head toward a fabled empire of riches that no outsider has ever seen, intent on looting its great treasures. And toward the same legendary land stumbles the lost James Blake, an American whom Tarzan has vowed to rescue. Following their spoors, the ape-man comes upon the lost Valley of the Sepulcher, where Knights Templar still fight to resume their holy crusade to free Jerusalem. Soon Tarzan, the true lord of their ancient motherland, finds himself armed with lance and shield, partaking of jousting and ancient combat. And then it is that the slavers strike!