Carter, the actual author, claims to have merely edited the manuscript, which, like subsequent works in the series, supposedly found its way to him from the ruins of the ancient city of Arangkhôr in Cambodia.

Dark, a helicopter pilot transporting medical supplies in Southeast Asia, is forced down in the jungles of Cambodia, where he discovers Arangkhôr.

The world in question is eventually determined to be the Jovian moon of Callisto, which beneath a projected illusion of airless desolation turns out to have a breathable atmosphere, an alien biology, and human inhabitants (presumably descended from victims of the well during the period before Arangkhôr was abandoned).

After nearly falling victim to a Yathib, one of the local predators, Dark is saved by a nomadic tribe of Yathoon, a race of intelligent insectoids.

Fleeing the city, they restore Darloona to her people, the Ku Thad, who have been living in the jungles of the Grand Kumala since their exile from Shondakar.

Reviewing this book along with the following two volumes, Lester del Rey found the series to be "fairly entertaining reading," but noted that Carter had "copied every trick of Burroughs, including those that are faults.

On the down side, he views Jandar as "kind of an arrogant jerk ... a bit of an egotist ... constantly getting into trouble with half baked plans [from which he] is regularly rescued by his friends or saved by dumb luck."