Die Lexx ist in der Umlaufbahn der beiden kriegsführenden Planeten Feuer und Wasser gefangen. Die Crew macht Bekanntschaft mit dem charismatischen, aber bösen Prince. Die beiden Planeten umkreisen einander und es existiert ein atmosphärischer Tunnel zwischen den beiden. Die Einwohner von Feuer attackieren den Planeten Wasser ohne ersichtlichen Grund. Die Beherrscher von Feuer sind Prince und Duke. Wasser scheint keinen Herrscher zu haben; die geringe Bevölkerung lebt auf schwimmenden Inseln.

The Lexx is running out of food and must fly slowly to conserve energy. 790 computes that it might take thousands of years to reach an inhabited planet. The crew enters cryostasis to survive the voyage. After 4,000 years in cryostasis, they reach the twin planets Fire and Water. The entire third season takes place on these two planets.

The crew meets people they knew from the Light Universe. These survivors cannot remember their past in the parallel universe, though their personalities are still the same. Fire is ruled by the charismatic Prince. Water doesn't seem to have a ruler. The inhabitants of both planets live in isolated towns. On Water they live on islands in a huge ocean and on Fire, there are massive towers separated by long stretches of desert.