 Tarzan, his monkey friend Nkima, and Chief Muviro and his faithful Waziri warriors prevent Soviet communists from looting the lost city of Opar.The story also prominently features Tarzan's lion ally Jad-bal-ja.This book marks the last appearance of Opar and La in the Tarzan series, aside from the juvenile piece "Tarzan and the Tarzan Twins with Jad-Bal-Ja the Golden Lion" (1936), which was published later but is chronologically earlier.