While exploring a mysterious dinosaur bone yard, Roxton is attacked by a charging Ttriceratops and kills it, not out of necessity but in anger. However, the bone yard is actually a sacred animal burial ground, protected by a beautiful, half-human, half-dinosaur guardian named Oseena. To punish Roxton for his crime, Oseena curses him to become the prey in a hunt that will end only with his death. Shaken by his encounter with Oseena, Roxton returns to the treehouse, but the hunter tracks him relentlessly and then captures Marguerite, using her as bait to lure Roxton into a deadly trap. Roxton returns to Oseena's burial ground to confront the hunter and save Marguerite.

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.

When Challenger discovers the wreckage of a World War I transport plane, he's captured by its pilot, Lieutenant Drummond. Drummond has been stranded for five years since the crash, protecting the plane's cargo—a crate of iridium ingots stolen from the Royal Navy. Challenger is astounded to see the iridium because it had been intended for his secret wartime research. The sight of it prompts him to remember the night five years earlier, when he was questioned about the theft by two British intelligence agents working for MI5.

Back on the Plateau, when Challenger and Drummond arrive at the Treehouse, Marguerite recognizes the iridium, too—she also was a suspect in its theft, and she recalls her own MI5 interrogation, the same night Challenger was questioned.

Amazing twists and turns. We find out that there may be more than just coincidence that has brought our small group to the plateau.