
Summerlee opens the map from Challenger, finding it blank, at which point Challenger appears from nowhere leaving Summerlee no option but to accept his guidance on the exhibition. The expedition arrives in Africa where they are joined by a female guide named Malu and a Portuguese called Gomez. A newsboy associate of Malone named Jim stows away on the trip.

With obvious reluctance, Challenger gives Summerlee a "map" to be opened at a road-end village in Africa at a particular date and time. Summerlee agrees to Malone and Nielson coming on the expedition, but refuses to allow Challenger to be part of the expedition. After receiving funding from the family of Jenny Nielson, a wildlife photographer and the daughter of a rich American contributor to the sciences, the "scientific community" agrees to organise an exploratory expedition under the leadership of the antagonistic Professor Summerlee. The British scientific community finds his claims laughable. Challenger has a picture of a cliff and a strange beast resembling a pterodactyl that is his only evidence of the place.
Malone is sent to interview Professor Challenger, an explorer and researcher who believes he is on the trail of the "lost world," a mysterious place in Central Africa. The film opens on Edward Malone, a junior reporter looking for an adventurous assignment.
