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.