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 a lost archaeological expedition discovers a mysterious burial urn, the young student who opens it suddenly collapses in convulsions. Though she quickly recovers, Professor Hamilton, the expedition's leader, suspects she's contracted a disease from the urn's skeletal remains. He believes that's the only rational explanation for the inscription on the urn, warning that an evil demon is imprisoned within.

But the next day, Roxton and Marguerite discover the expedition's camp has been torn apart, and that of all the archaeologists only two survive-Hamilton and his rival, Professor Campbell. In a tense standoff, the two men claim the other is possessed by the demon. Roxton's and Marguerite's intervention only succeeds in making the archaeologists suspect the demon has jumped into one of the two explorers.

Challenger, Roxton, and Marguerite take Finn to a cave where one year earlier a blinding light opened a doorway to another reality. Once inside, the explorers witness an eerie apparition of a man Finn recognizes and fears.

But when Finn races from the cave, the three figures who follow are not her friends-they're Kayle, Una, and Rixxel, three demons who have taken the place of Challenger, Roxton, and Marguerite. If the demons can remain on the Plateau for two days, they will permanently replace the explorers, and Kayle will be free to bring chaos and destruction to the world.

In the final deadly showdown between Finn and the demons, Finn must make the decision of her life-save the future or save her friends. Until an unexpected sacrifice changes everything…

Hoping to end starvation, Challenger becomes the first human subject to test his new experimental substitute for food. But his nutritional beverage is not as successful for him as it was for his lab mice, and he quickly becomes obsessed with discovering the reason why. Then obsession leads to madness as Challenger is confronted by two opposing hallucinations. The first is a vision of himself as a young, driven scientist. The second is his beloved wife, Jessie, as he left her in London three years earlier. Unconscious and near death, Challenger is finally discovered by his friends. But will their limited medical knowledge be enough to reverse the ravages of his experiment, without placing him in even greater peril?

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.

Led by a dream, Veronica touches her mother's pendant to a stone monolith. A flash of mysterious energy knocks her unconscious, causing her to relive her last days with her long-lost parents as a young girl. When she awakes, she's shocked to realize her new memories don't match what she's always remembered of that time.

With the fate of her parents no longer unknown, Veronica is at peace, though she realizes a larger mystery is still to be revealed-her mother's pendant is somehow the key to her own destiny… and that destiny is fast approaching.

A peaceful day of exploration turns deadly when a sudden explosion traps Marguerite and Roxton in an underground chamber. Their only hope for escape is Challenger, but the same explosion has left him with no memory of who he is, or what has happened to his friends.

Meanwhile, a contest of friendly rivalry between Veronica and Finn leads to an enigmatic discovery at the Treehouse, as another memory from Veronica's childhood is literally uncovered.

Faced with certain death, Roxton and Marguerite reveal emotions best left buried, so that even if they do survive their ordeal, there's a chance their relationship will not.

Two days before Challenger's latest attempt to leave the Plateau by balloon, Veronica and Finn encounter a strange phenomenon and are briefly transported into the post-apocalyptic future of New Amazonia. Soon after, Roxton finds himself being chased by 17th-century Conquistadors while Marguerite is captured by Druids determined to sacrifice her in order to avert a mysterious storm which is fast approaching.

As different planes of reality continue to collide, Veronica at last realizes the time has come for her to fulfill her destiny as Protector and wield her mother's pendant-the Trion. But even as she prepares to sacrifice her life to save her friends, she does not know if she's made the right decision-for once the power of the Trion is unleashed, will it save the Plateau, or destroy it… ?