Tarzan searches for Erich von Harben, the son of an old missionary friend who has disappeared while exploring remote mountains. The trail leads to two rival cities whose inhabitants claim descent from ancient Romans, drawing both Tarzan and von Harben into arenas, political rivalry and escape attempts.
The search begins in the interwar world of missionaries, archaeology and African exploration before opening into Burroughs's fantasy of Roman colonies surviving in isolation. Ancient political forms, arena combat and rival cities are set against the modern expedition that discovers them, making the contrast between past and present the central fascination of the adventure.
