The dense forests and forbidding jungles of Africa harbour innumerable uncanny mysteries, dangers and horrors.

Among these, often reported though little known, is a secret society of Leopard Men. By day and night they are the terror of the vast domain they frequent. Their orgies, their rites, their ruthless power form the basis of this series of adventures, of which Tarzan of the Apes is the central figure.

Adding to the suspense, an absorbing detail of interest is the mysterious quest of a beautiful American girl braving the dangers of the Dark Continent alone; while nonetheless interesting are two luckless and poverty-stricken white ivory poachers, whose trails cross those of both the Lord of the Jungle and the lone girl - trails that lead three of them to the forbidden precincts of the Holy of Holies of the Leopard Men, where no white man has ever been and returned alive.