Tarzan (Bruce Bennett) is in Guatemala (although still with African animals around) and is helping Major Martling (Frank Baker) and Ula Vale (Ula Holt) steal - sorry put into safety - the idol of a Mayan tribe. The idol contains the secret formula for Mayan explosives which could become the ultimate weapon...
Raglan (Ashton Dearholt) meanwhile is also trying to steal the idol and formula for more nefarious ends. Plus the natives are trying to get their idol back and we get a regular to and fro struggle. The film is an edited version of a serial which means it has plenty of cliff hangers though requires a few plot summary title cards throughout to explain the rather jumbled plot.
If you can get over the geographical nonsense, plot that is all over the place and dated stereotypes it isn't a bad adventure film. Tarzan is more "civilised" than in some other films though still looks the part and can swing from trees!