Global warming has led to the melting of the polar ice caps. Sea levels have risen dramatically, with devastating effects. Survivors Richard and Amy Webber of environmental pressure group Greenwatch are teaching children the skills they will need to help restore the damaged planet.

Richard and Amy are arrested in a Commission raid on the school, leaving their own children, Greg and Karen, to fend for themselves. They join Ash and Mai-Li to find Goodman, an old associate of the Webbers, at his laboratory within a derelict mill. Goodman recounts the history of Greenwatch, explaining how its outlawed scientists have been blamed for causing the disaster they had tried to prevent, and the children return to the school for medicine to treat his illness.

At the Commission Headquarters, telepath agent Kurt Glemser interrogates the imprisoned Amy Webber in a malevolent attempt to locate and arrest the missing telepathic children, who he refers to as 'senders'. Amy tries to send a warning message to Mai-Li through her own telekinesis abilities, but she is too late; eventually realising that herself and Ash are in imminent danger, Mai-Li is then faced with altering Goodman's memories before Glemser forces him to betray her.

Goodman is requested to treat an aggressive Japanese leaf worm disease that has apparently broken out on a farm, affecting its crops. After the group arrive, it transpires that the unscrupulous owner of the farm, Harry Fellside, is using illegal, highly toxic nerve agent chemicals to promote the growth of his plants, and ruthlessly forcing his captured 'climeys' (climate refugees) that have migrated from a similarly-flooded France into brutal lives of slave labour exploitation.

The children respond to a distress call from Loppergarth Island. When they arrive, they find Loppergarth Island deserted, save for Gemma, a sleep-deprived young girl in shock after a week of compulsively trying to stay awake. They eventually ascertain that her parents and the rest of the populace have been consuming contaminated gull eggs, causing them to fall under a shared hallucination and gather to become comatose in the village church for an otherworldly crystal entity.

Having ran out of fuel while at sea, the children are given no choice but to moor their boat on the nearest possible island. Whilst there, they discover a museum dedicated to preserving parts of the time before the floods, looked after by a strange middle-aged woman with a literal 'eye socket' named Polly Phemus. Upon trying out her old virtual reality video games, it becomes clear she is trying to trap them, and the group strive to break out of the virtual world and get back to real life.

In need of an old car part to power Goodman's broken electricity generator, Ash and Greg travel to the Cartmel scrap market. The boys find the part for sale, however its owner demands too high of a price. They decide to try their luck at Devil's Island, a mound of land largely consisting of a giant scrapyard. While looking around the site, they discover that it is inhabited by numerous feral, mutant dog-like children of varying morality, living as a pack amongst the vast waste.

Joshua, a young 'sender' who has been arrested by The Commission, appears to go missing while under their authorised escort transference. Now a fugitive seemingly looking for help from the children, it is eventually revealed that the boy and the Greenwatch personal computer have been programmed with a life-threatening psychic virus by Dr. Galina Renkova, developed by him with malicious intent to make the telepaths progressively attack and destroy one another.

Greg sets off to replenish the group's supplies of a vital plant ingredient needed for sunblock, essential in the new climate. During his search trip, he meets a mysterious, attractive brunette, Siren, who appears to have the plant he needs. Through her, Greg finds himself caught up in the sinister activities of a strange sun-worshipping cult, who are determined to put a stop to people they perceive to be 'interfering' with nature and what is seen to be its natural course.

Greg takes a bored Mai-Li and Ash on a boat tour around the nearby islands to avoid staying cooped up indoors. They subsequently receive a morse code message from Paradise Island. Heading there, they discover and attempt to help old island resident Hepzibah McKinley, a scientist who claims to have discovered the secret of cold fusion, and is continuing her father's incomplete research into the subject to try and create greater sources of energy for the remnants of the world.

Greg and Mai-Li investigate an empty dinghy, drifting away in the sea. Suddenly drugged and kidnapped, Greg wakes up in a house with no memory of the prior events, and a young girl, Marianne, tells him that he was found floating alone. Unbeknownst to Greg while he is looked after, her father, Professor Peterson, plots to experiment with and ultimately sacrifice a captive Mai-Li in an attempt to cure his daughter of the rapid-ageing condition that she is actually suffering from.

Goodman takes Ash to the Cartmel scrap market for video spares. Ash meets Luke, another 'sender', and is lured to fall in with Skylar, a Fagin-like crook who convinces young telepaths to steal for him. In return, Skylar provides them with Tags, dangerous chemical strip patches that can stimulate and enhance their telepathic abilities at the risk of serious side effects. Before he can stop using them, Ash comes perilously close to burnout and health complications.

Amy appears to escape from The Commission's headquarters, and makes her way back to the base in an attempt to be reunited with her colleagues and family. However, she starts to show more unusual concern for the current whereabouts of the two 'senders', instead of her own children.