Challenger, Malone and Veronica are exploring ruins on a riverbank, when a man stumbles out of the jungle in a hail of deadly arrows. Malone drags the wounded man to safety, who dies in their arms issuing a cryptic message to find a man named Pierson Rice. Challenger recognizes the name as that of a vain glorious hunter whom Roxton once held in high regard. The trio send a message to Roxton and Marguerite, then hurry on in search of Rice. Roxton is disgusted to learn that his one-time hero may be alive and well. Arriving at a native village, our heroes discover that Rice is far from peril -- in fact, he has made the natives his loyal subjects. With the help of his cold-hearted lieutenant, Rice plans to eliminate the queen and marry her beautiful daughter to consolidate his power.

Using the Plateau's mysterious energy lines as a source of power, Challenger constructs a machine to send the explorers back to London. But when he, Roxton, and Marguerite find themselves in the same place they started from, they conclude the machine is a failure and head back to the Treehouse-only to discover the Treehouse is gone!

While investigating what else has changed, Roxton is captured by slavers with automatic weapons and stripped-down cars, and learns the shocking truth-he and his friends are in the year 2033, eighteen years after an apocalyptic war devastated every place on Earth except for the Plateau.