Roxton is looking for the materials for a crossbow to bag a T-Rex, but when one actually interupts him in his labors, he runs in the direction opposite his fellow travelers to keep them safe. He winds up falling into a hole that suddenly opens up. When the rest of the group search for him, they also fall into the hole, which turns out to be a whirlpool. It sucks them all under the water, and they emerge in a lake. They quickly find out that in this part of the plateau, the dominant species are lizard-like men, descendents of dinosaurs, and the humans are subservient to them. There is an ancient Roman structure to this civilization, including gladiator-type battles. While Marguerite and Veronica are forced to change into silky gowns for the entertainment of Tribune, the lizard-people's leader, Roxton is chosen to fight another human prisoner. The slaves and travelers rebel, and overthrow the lizard-men's intolerable rule, but not without loss ~ Roxton's opponent's sister ~ a rebel leade

Veronica and Summerlee are out gathering fruit and floral specimens when they are attacked by a huge bee, one the size of a man. Summerlee is stung, and it leaves him near death. The only cure is the nectar in the heart of the hive. Veronica, Malone and Roxton travel to the hive, leaving Challenger and Marguerite behind at the treehouse to care for Summerlee. Summerlee is delirious with fever, and imagines Marguerite is his long-dead wife. She plays along, to sooth him. In the meantime, Veronica, Malone and Roxton do make it to the hive, work their way deep into it, gather nectar, and head back quickly to the treehouse, just in time to save Summerlee's life.

The aged guide who brought Veronica's parents to the Lost World dies in Challenger and Veronica's arms, humming ""Ode to Joy,"" leading the explorers to seek out a hidden paradise, where Veronica suspects her parents might be.