Ion Idriess shares with his readers yet another rich deposit of fascinating information he has uncovered on his wanderings in the 1920s. He is not content to pick up what lies on the surface, but delves into strange places, not only in the wilds of Australia and New Guinea, but in the shadowy regions of the minds of the primitive.

Idriess investigates the mysteries of the cave paintings of the Kimberleys and the powers of telepathy exercised by the natives of Cape York Peninsula and the Torres Strait islands. Most fascinating of all, perhaps, is the picture given of swamp life in Northern Australia and on the mighty Fly and Sepik rivers of New Guinea, where a thousand-mile voyage is made through the eerie and terrifying world of the "Sea of Swamps" to the hidden villagers of the headhunters.