After the policeman left, Ned and Challenger returned to the house, where a furious Mrs. Challenger was waiting. She called her husband a bully for his treatment of Ned, but once she saw that Ned was safe, she calmed down. Her husband and Ned returned to the professor's study to continue their conversation.

Challenger explained to Ned he felt Ned had some good feelings toward him, because he took responsibility for the fight. He also told Ned he will tell him the story of his adventure in South America, as long as Ned promised not to publish a word of it without his expressed permission. Ned did not like this condition, but he went along with it.

It seemed Challenger was on a trip to explore the Amazon River, when he encountered a tribe of Cucama Indians. They were kind to him and in return he used what medicines he had to help heal some of the sick and injured in the tribe. On his return back up the river these same people were waiting for him, which he thought was because they were happy to see him again. The truth was they were once again in need of his medical services.

A white man had staggered into the camp exhausted and near death, and by the time Challenger reached him, the man had died. Challenger found the man's knapsack, which had his name on it. He was Maple White of Detroit, Michigan and he also had a sketchpad with him. The sketchpad was in sorry shape, but it did hold a number of sketches. Most were of native people and scenery along the Amazon River, but at the back of the book was a sketch of an animal like none ever seen by humans. This sketch caught the attention of the Professor and he used the sketches of the land to determine where the drawing of the animal was made.

The professor convinced the natives to take him to this place. They did not want to go, because it was in a part of the forest where terrible spirits were supposed to live. Once he was able to secure two guides, they traveled there and saw for themselves some most unusual creatures. Challenger was able to produce some physical evidence for Ned to see; one piece was a wing of some sort. It looked similar to a bat wing, except it was larger than a bat wing and it was shaped differently. It did look like a pterodactyl wing pictured in a book he showed Ned. He also showed Ned two badly damaged pictures of the area drawn in the sketchbook.

The whole area is surrounded by cliffs, which the professor felt cut it off from the rest of the world, so the changes which caused other creatures to die out did not affect those living there. Ned is convinced the professor is telling the truth about his discovery. Challenger asked Ned to attend a lecture at the Zoological Institute to see him make a few remarks, after the main lecturer had spoken.

Ned's editor, McArdle, was not happy about his report. He could not believe Ned accepted Challenger's story, nor could he understand how Ned would agree not to write a word of what Challenger said. He did insist Ned write an article about the events which occur at the Zoological Institute meeting that evening. Ned agreed to this because it is a public event, so Challenger could not censor what he writes.

Ned had dinner with Tarp Henry to tell him about his interview with Professor Challenger. Tarp was very skeptical about Challenger's evidence. He thought Professor George Challenger had drawn the sketches in the sketchbook and faked the photographs. Ned was beginning to question his own conclusions about the veracity of the professor's claims. Ned asked Tarp to accompany him to the lecture, so both of them might judge the professor again.

At the lecture hall they found a large contingent of people already there waiting for Professor Challenger to make his appearance, many of them were medical students, who were in a boisterous mood. The lecturer was Mr. Waldron who gave a talk on the formation of the world.

During the lecture, whenever Mr. Waldron would speak of extinct prehistoric animals Professor Challenger would call out "question". Mr. Waldron did his best to laugh off this behavior or to totally ignore the outburst. It did disrupt the lecture though and caused Mr. Waldron to become distracted.

Finally, it was time for Professor Challenger to make his motion to thank Mr. Waldron. Instead, Challenger used his time to discredit the lecturer's stance that prehistoric animals were extinct. He was shouted down as a liar and told to prove his assertions.

Challenger answered these calls with a call of his own, a call to form a committee to test his findings. He asked for one or more of those assembled to go to South America and find the animals he claimed were there. Professor Summerlee, Professor of Comparative Anatomy volunteered, as did Ned Malone and Lord John Roxton, who is a sportsman and a traveler. At first the other two did not want a member of the press along on the adventure, but Professor Ronald Murray, the chairman of the Zoological Society, decided it might be beneficial to have a reporter along on the expedition. After the lecture Lord John Roxton asked Ned to his rooms so he might have a word with him.

Ned had gone from believing Professor George Challenger was a fraud to believing in him and back to questioning his judgement of the man. He had also found his great and dangerous deed in an expedition to South America. Challenger was also getting the chance he sought, to prove to others the truth of what he has been saying about the animals in South America.