Several plot elements bring the characters together in search (and pursuit) of the Guatemalan idol known as The Green Goddess: Tarzan's friend D'Arnot has crash landed in the region. Major Martling is leading an expedition to find the fabled artefact. Ula Vale's fiance died in an earlier expedition and so she starts one of her own in his honour. Raglan has been sent by Hiram Powers, Ula's lawyer, to steal the valuable idol for himself - in addition to containing a treasure trove, the idol is also said to contain an ancient formula for a super-explosive that could prove very valuable and very dangerous.
Tarzan and Major Martling find the idol and rescue D'Arnot from the natives that worship it. However, Raglan escapes with the Green Goddess and heads for the coast. Tarzan and company, joined by Ula, pursue him across the jungle, out to sea and back to Africa in an attempt to stop him and reclaim the idol.