Drought conditions in Haven are at a crisis point. Desperate to give the precious animals the best chance for survival, Arushka and the Nomads attempt to muster them from the vast, parched high country into the lowlands. A scrub fire breaks out and the frightened animals are scattering when Myah and the brothers appear offering help. Together with the Nomads they manage to put out the fire and herd the animals to a lowland area where there are still a few patches of pasture.
Arushka and Noah warily agree to hear Myah's suggestions for a more permanent solution to the drought. She explains that in Silver City of 2235 their father was in charge of a weather control system and that they have landed here as a result of Rorden's fallible experiments with time-travel. Rorden unveils the futuristic blueprint for a rain machine and Noah is astounded to realise the building of such a thing is feasible. But with Thunderstone eradicated from Haven there would be no source of power gigantic enough to drive this machine from the future.
Back in North Col, Becky discovers a storeroom filling with steam. She is struggling with valves and overrides switches when Liz, her mother, comes to the rescue. Something is wrong with the exhaust line, which Liz believes could indicate serious problems with North Col's foundations.
In the Haven compound the Nomads are mulling over the impasse with the rain machine. Monsoon arrives with tales of a distant valley, high in the mountains beyond, where the Nomads have ever ventured. Legend has it that it is home to a huge cube of pure Thunderstone. The Nomads agree on an excursion there. They have to find out if the Thunderstone cube is more then a myth. It could be the key to saving the animals.
The relentless trek upwards in the heat seems to be fruitless. The thirsty Nomads eventually find the mystical Valley of Chazon, but instead of a Thunderstone cube, there is a great lake in the valley floor. Arushka collapses by the shore in despair when she discovers that the clear blue lake is salt water.