A vampire bite elevates Roxton's hunting instincts to a bloodthirsty level; a smitten native will fight Malone to the death for Veronica.

Scientist and explorer George Challenger learns from a dying colleague of a prehistoric world and organizes an expedition to find it.

Stung by a giant bee, Summerlee lies near death; Challenger seeks a way to repel an attack by the ape-men.

When a powerful witch named Dame Alice feels threatened by Challenger's science, she calls upon her two beautiful acolytes to help undo his power. In order to earn full witchhood, the two must lure Challenger's ""guards"" - Roxton and Malone - to the witch's castle while she goes head to head with the ""wizard"" - Challenger - herself. While the two young witches distract Roxton and Malone, Dame Alice visits the Treehouse for a visit. In spite of Marguerite's protests and warnings, Challenger is intrigued by the witch's power and too easily lowers his guard. When Dame Alice sabotages Challenger's newest invention and almost kills him, it is only Marguerite's quick thinking that saves the scientist from his own folly. But in the end it is not Challenger's life that is in danger, but the lives of Roxton and Malone….

Ambushed in the jungle, Roxton narrowly escapes with his life only to learn that he has apparently cheated death once too often. The Grim Reaper, in the guise of a dark seductress - is determined to add his soul to her collection. Transported to her domain - a bleak and desolate wasteland - Roxton must face a series of challenges if he hopes to get out alive. And to make the game more interesting, Death raises the stakes by putting the lives of his friends on the line as well. Confronted by shifting rules and deception, Roxton cannot hope to win. At every turn, Death torments and goads him, encouraging him to abandon his friends to save himself. Round one goes to Death, rounds two and three as well, and with growing horror, Roxton loses Challenger, Veronica, and finally his beloved Marguerite to Death's netherworld inferno.

Desperate to escape and more than a little greedy, Marguerite offers Veronica to a tribal chief in return for jewels and safe passage off the plateau for her group.

When Roxton is running from a tyrannosaur, the earth suddenly swallows him up; the party follows a river to an underground ocean.

Christecs brand Summerlee a devil after he revives a drowning child.

When a blindingly bright meteor strikes the Plateau, Challenger, Roxton, and Marguerite set out to investigate the impact site. But the closer they get, the colder the temperature becomes. As the explorers turn back, they discover what appears to be a victim of the intense cold - a beautiful, blue-skinned woman, unconscious and nearly frozen. To save her life, the explorers take her back with them. When the frigid temperatures reach the Treehouse and all attempts to warm the woman makes her condition worse, Challenger suspects that things are not as they appear. Roxton and Marguerite are attacked by a group of blue-skinned male warriors and the truth becomes clear - the heat-absorbing meteorite now buried in the Plateau is the first step in a terrifying invasion of creatures who need the cold to survive.

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…

In order to free Challenger from her tribe, the team must retrieve the bones of a warrior queen's husband.

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?

Roxton changes the lives of the Tintas when he kills a warrior from the Hikari tribe; a World War I flying ace crashes in the jungle and takes Marguerite, Malone and Summerlee as prisoners.

Veronica unwittingly releases a savage giant from captivity, and Marguerite and the others must use all their talents to subdue him.

When Keeran Raiders attack, a deadly poison dart forces Malone to relive a long-suppressed memory-his baptism of fire as a battlefield correspondent in World War I. Caught up in this nightmarish hallucination, Malone is once again an untried reporter cut off from Allied lines when an enemy advance pushes deep into No Man's Land. When the three battle-weary British soldiers who've been assigned to escort him are picked off by enemy action, the young reporter who's never fired a gun must take up arms to save his own life and the life of a wounded sergeant.

Alone in the jungle, Veronica hears piano music and follows it to its source - a 19th century German village that has suddenly appeared in a fog choked valley. To her surprise, the handsome musician, Thomas Ducart, announces that he wrote the beautiful melody for her. Flattered by the musician's attention, Veronica takes him to the Treehouse, but Challenger is concerned. He fears that Ducart's village may be unstable, and Veronica could disappear into another dimension if she returns to the village with Ducart. Even more disturbing, are Challenger's ill feelings about Ducart's designs on Veronica, but Challenger's warnings only drive the beguiled Veronica further into Ducart's passionate embrace.

Challenger, Malone and Marguerite find a subterranean civilization after being trapped in an abandoned mine.

Ramses, a vivified mummy, enlists Marguerite, Challenger and Malone to help him regain the Egyptian throne; a grieving dinosaur targets Summerlee.

An unsettling dream and a ghostly encounter convince Veronica that Malone is trapped in the spirit realm and needs her help to escape. At the same time, Assai and Challenger investigate a mysterious symbol burned into a field of grass, which Assai identifies as the mark of Saros, a bloodthirsty warlord who was overthrown by the Zanga and died swearing to return from the grave to wreak vengeance on the living. Back at the treehouse, Marguerite and Veronica use a Ouija board to contact Malone, which results in a frightening display of poltergeist-like activity, and a brief, but terrifying manifestation of Saros. Assai is convinced that any new attempt to rescue Malone from the spirit realm threatens to release Saros instead.

Challenger develops a new way to create lift in the balloon. All go along for a test flight, but the balloon is drawn into violent turbulence then crash-lands inside the vast caldera of an extinct volcano where our heroes find themselves trapped in a world beneath the earth's surface. With the balloon damaged and the supply of iron lost, our heroes can only survive for a matter of days in this hot and hostile environment. Aleece, a strong-willed female warrior-in-training, hurries to the rescue. In exchange for a ride in the balloon she offers to help replenish the iron that is needed. Malone accompanies her to a mine, but instead of raw ore, her plan is to steal from the supply of a vengeful exile named Arjax. After being caught by Arjax, Malone and Aleece face death unless they lead Arjax back to the balloon.

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.

Druids worship Marguerite, who bears the mark of an ancient prophet; Veronica and Summerlee find a baby.

Roxton, Challenger and Summerlee bring badly injured Malone to a magic healer in order to save his life.

The adventurers come upon the ruins of a civilization destroyed by an enormous explosion.

Veronica reunites with her father; the team must fight Kartas, a bounty hunter after Veronica's father.