Aluna and Hoku, ocean-dwelling Kampii, are in danger so long as they are in the Above World, especially in the desert. They and their friends are racing to the city of Mirage to stop the Equians from joining Strand and Scortch's army--the problem is that Strand has gotten to the Equians first, and they are going to war in their name. The only hope Aluna and Hoku have now is to win the fabled Thunder Trials, gaining the prestige to change the Equians' minds.