The plateau is threatened with destruction as the explorers encounter a baffling new phenomenon. We are left with a cliffhanger that ends the series and never returns.

An explosion traps Marguerite and Roxton in an underground chamber, and 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.

When the man that wants ultimate power over the plateau receives the medallion from the assassin who appeared in 'The Secret', he goes to the plateau and Veronica ends up reliving the last days she spent with her parents in various visions.

Roxton's wartime record is exposed by a stranded enemy agent, who has also been trapped on the plateau. Plus some other secrets about Marguerite and Challenger come to light.

Challenger gets trapped in a life-or-death duel with apparitions from his mind, when an experiment with an elixir he makes, goes very wrong.

New characters enter the plateau and it would appear that one of Challengers team now might be possessed by the Devil.

Our adventurers, are now joined by Finn from 2033. Claims of demonic possession make everyone a suspect, when a team of archaeologists are killed on the plateau.

Challenger experiments with a mysterious energy source, and Challenger, Roxton and Marguerite are thrown forward in time, approximately 100 years to 2033. On their return they are joined by a young woman called Finn.

A rift between Roxton and Marguerite begins, when an assassin linked to Marguerite's secret turns up and threatens the explorers lives.

Veronica goes for a walk and is drawn toward some piano music that she can hear, walking through a mist she comes out in a village 100 years in the past, where she falls in love with a 19th century musician, unaware of his obsession.

A beautiful woman, determined to claim Roxton's soul, turns out to be Death himself.

A deadly new ice age which threatens the world, is set in motion, as a mysterious meteor plunges into the plateau.

Malone and Challenger get attacked by a tribe with blowpipes and darts that may cause death, and Malone ends up reliving his suppressed memories of World War I.

Challenger's scientific knowledge is put to use - when up against a powerful witch bent on destroying him and his science.

Challenger "upgrades" the adventurers balloon and the gang go on a test flight. They crash in an unforgiving land, where Malone befriends a female warrior.

Roxton gets stuck in the old west, pursued for a crime he didn't commit.

Marguerite and Roxton travel up river to save their friends from Roxton's former mentor.

Malone becomes the link between a knife and the infamous murders by Jack the Ripper.

Challenger and his team risk unleashing a supernatural killer to save Malone by holding a seance, which originally is started by Marguerite and Veronica's use of a Ouija board.

While exploring a dinosaur bone yard, Roxton disturbs an animal grave site and is punished by the guardian Oseena to be the prey in a hunt to the death.

A trio of dashing bandits with a deadly secret appear on the plateau, and Marguerite joins up with them.

The story of the airship continues with a deadly airship crash, that traps Challenger and company seven years in the past.