With the support of a mysterious funder, Professor George Challenger assembles a team to go after evidence to prove that prehistoric creatures are still alive. On their journey they encounter harsh weather, exotic flowers, violent natives, and all kinds of formidable creatures old and new. They cross paths with a jungle dweller who soon becomes an ally. She warns them to go back to their land for their safety, and tensions rise as it becomes clear that members of the group may have different motives.

Equipped with enough research material and evidence to return home, the adventurers prepare for their journey back to London. Marguerite makes a duplicitous trade with Chief Jacoba, involving Marguerite and an arranged marriage. In return, the Chief promises that the group will have safe passage off the Lost World plateau, but a series of unfortunate events leaves them back at square one.

Everything the adventurers have known about society is lost in this world where humans are at the bottom of the hierarchy and must battle each other for survival. The reptilian race that holds them captive sees humans as only beneficial for labor, reproduction, and entertainment. Tribune is intrigued by the science and technology Marguerite introduces him to, and the adventurer's passion for freedom is instilled in the other enslaved humans.

Professor Summerlee is attacked by a massive bee and poisoned with deadly venom. They seek out a healer from Veronica's childhood who knows the whereabouts of the antidote, and find that it's at the center of a bee hive no human has ever made out of alive. Meanwhile, Challenger and Marguerite keep the ape men away from the tree house with the help of electricity. Veronica, Roxton, and Malone venture into the hive to retrieve the antidote but what they come across leaves them disenchanted.

Challenger breaks a sacred taboo while searching for sulfur and is taken hostage by a native tribe. The adventurers must now retrieve the tribe king's bones from the Cave of Fear in exchange for Challenger's life. Roxton and Marguerite must face their troubled pasts when they venture into the cave, and it's up to Summerlee--the most frightened in the group--to save his two comrades from their own fear.

Summerlee saves a village child from the river, convincing the village leader that they're all witches. Veronica flees to warn the others, while Challenger attempts to convince the village council of modern science to prove the action was not witchcraft. Marguerite and Malone get into a heated argument about his journal, but they put their differences aside to save the others from being burned at the stake.

Roxton gets bitten by a by a diseased man and starts to thirst for blood, while back at the treehouse a village man wants to pay Malone for Veronica to be his wife (or fight him to the death for her). Veronica has to resort to a drastic action to show the men that she doesn't belong to any one of them. Roxton becomes more ravenous the longer he's transformed and attacks his comrades. Challenger and Marguerite poison him in the hope that it will rid him of the infection.

Marguerite's birthmark is a visual confirmation that she is the reincarnation of the Druid's priestess whose destiny is to seek out the emeralds that will save them. Dinosaurs, quick sand, head hunters, and shape shifters come in their path only to put them in the right direction of the sacred jewels. In the meantime, Veronica finds a baby in the forest and takes him home while Challenger and Summerlee try to find the child's parents.

Veronica comes across her parent's guide, Sinta, and has renewed hope for finding them. The explorers come across a land of paradise where the inhabitants are all young, lively, and serene on their search for Veronica's parents. Roxton's suspicions of this land is confirmed when it's revealed that civilians are sacrificed so others may live immortally. The fruit they eat comes from a tree that feeds by draining humans' life essence. They must find a way to take down the tree and save Malone from the draining effects it had on him.

A village healer saves Malone from deadly poison, which in turn fills the healer with the spirit of a demon. The healer is set to be executed, but Malone's guilt influences him to help the possessed healer escape. The girls find themselves stuck in a deep ditch after being chased by a dinosaur, and they must learn to trust each other and and work together to get out. Malone goes after the healer, while Summerlee helps birth the new village shamen.

Challenger, Malone and Marguerite get trapped inside of an old mine shaft when an earthquake caves them in. Veronica, keeping watch outside the mine, escapes and is able to rally Roxton and Summerlee from the treehouse to help rescue the others. Near death from lack of oxygen, they are saved by the Garza: an underground civilization led by a blind boy known as The Oracle. The Oracle calls for the explorers execution, but Challenger tries to warn them that they're all in danger as they're by an active volcano ready to blow.

The explorers come across the Tintas, a civilization that must pay the Hikari human tribute so that they are be left in peace and protected from other dangers. Roxton and Veronica teach them how to fight and retaliate against the Hikari so they may gain their independence. Summerlee, Malone, and Marguerite comes across a crashed plane. Malone fixes the plane while Marguerite nurses Dressler, the World War I pilot inside. Once Dressler wakes, he takes the explorers prisoner with the intention of killing Marguerite and escaping in his plane.

Malone, Marguerite, Challenger, and Roxton stumble upon the ruins of an ancient temple where they discover the crude etching of an atom dating back thousands of years. A ray of light knocks Challenger out, leaving the others frantic to save him. Challenger continues to live an alternate reality in his mind where he has gained the ability to manipulate the law of physics, but this newfound power changes Challenger and influences him to use his friends.

Marguerite is set to be betrothed to King Gawain. Roxton, Veronica, and Malone come to save her but get their weapons confiscated upon entry. They find out that the king's council, Vordred, is planning to kill him and take his throne. Gawain has them they retrieve the tooth from a T-rex to prove to the king that they're true of heart. Vordred shows his true colors and, upon his return, Roxton agrees to joust Vordred as Gawain's champion.

Challenger comes faced to face with an old friend from England, Dr. William Hargrove. It's revealed that Renata isn't his real daughter and that he's been feeding her false memories. Veronica investigates Hargrove's mysterious lab and finds that he has been genetically modifying the ape men. Summerlee, Malone, and Marguerite go after a mysterious woman who had showed up in one of their developed pictures. She's actually the queen of the nymphs and fairies stuck in a human body. They decide to help her break the curse.

While fishing, Malone, Challenger and Marguerite find a map off a dead man in the river and they decide to follow it in the hope that it's a way off the plateau. Summerlee, Roxton, and Veronica cross paths with a woman named Catherine while out hunting. It's revealed that her mission is to kill Marguerite as she ends up bringing a disease back to London that destroys half the world. Another individual from the future, comes to the lost world to make sure that Marguerite brings the plague back to the rest of the world.

Roxton, Malone, and Marguerite save a man named Tom staked between two trees. He claims to be Veronica's long lost father, escaped from slavery and on the run from a bounty hunter. But when the group takes Tom back to the treehouse to reunite with with Veronica, he reveals more sinister motives. The imposter uses a botanical drug on Challenger, Summerly, and Veronica so that they may protect him from an executioner sent for his head.

Summerlee touches a T-rex egg, which in turn has the mother tracking them for dinner. They go through great lengths to confuse and get her off their trail. Marguerite, Malone, and Challenger save a mummy about to be eaten by cannibals when they realize he's still alive. He enlists their help to take back his place as Pharaoh through manipulation. When they see that he's actually a malicious leader, they vow to fix what they've done.

Marguerite is kidnapped and Roxton is killed in an ambush, but a mystical boy gives him a chance to live and save Marguerite if he takes the life of another. The mystical boy's true intentions are revealed when the man Roxton plans on killing reveals that he's the child's jailer. Malone and Veronica save a man from a raptor, but quickly realize their mistake. He and his group of mercenaries chase Malone and Veronica back to the treehouse and demand them to hand the treehouse over to them.

Roxton and Marguerite save a young teen from an encounter with a group of Goths. They learn that he's the chosen one of the Moya; a civilization that was destroyed by the Goth and forced into hiding. Roxton is determined to deliver him to the elders because it was the final wish of an old dying man. Back at the treehouse, Veronica gets jealous when Malone starts spending time with another woman, and the other have a suspicion that she's infecting him.