The novel deals with the expedition of Hadon, a young Oparian warrior, to the Wild Lands and as far as the mysterious Ringing Sea, which would one day be called the Mediterranean, with the strange woman whom he meets and brings with him, and with the cataclysmic civil war which breaks out on his return and which he partly (and completely unintentionally) helps touch off.

A delicate balance between the genders is maintained, symbolized by the co-rule of the high priestess and the king (whose main authority is command of the army), which corresponds to some theories of sociologists and historians on the way actual matriarchal societies may have worked.

Lalila, the foreign "White Witch from the Sea," whom Hadon brings with him and with whom he falls in love, is used as a pawn in King Minruth's power game; the xenophobic suspicions aroused about her are used in an attempt to undermine the position of women in general.

Farmer seizes on Burroughs' ambiguity over the issue to recast Opar as a member city of an otherwise unknown local civilization that flourished in central Africa during the last ice age.

Eventually, subsequent to the period of his story, the two seas drain off into the Atlantic and the culture dependent on them decays and disappears, leaving only the remnant of Opar forgotten in the jungles where Tarzan will discover it.

While originally derived from the Tarzan series, the world created by Farmer is given its own independent literary existence, with the sociological and cultural aspects worked out in meticulous detail, and a long historical annex added at the end.