When the Professor's rival, Samuel T. Philander, visits Africa, he must come up with something spectacular to become famous on before Philander. That's when Tarzan tells them about Pellucidar, an underground world where dinosaurs live. However, Philander follows them there and takes pictures of the dinosaurs. The Professor, having no camera with him, attempts to best Philander by taking something else with him.

Tantor starts believe in an "All-seeing elephant" that protects him after he survives series of dangerous accidents. Tantor decides to journey to Mount Indigo, where the all-seeing elephant supposedly lives, to prove his friends the elephant truly exists. Tarzan, Jane, Terk, and the Professor decide to accompany Tantor to make sure he stays safe.