Aquatropolis is the most powerful city in the constellation.

But now, the Green Planet comes nearer, and with it, schemes and war are rising.

The rebels are trying to stop the corruption that has grasped the government, among them Alanna, who has escaped from court. Mermelle is determined to fight her manipulative brother Lyxéto, who seeks to gain power over Aquatropolis, and the city faces an attack that will be the beginning of a battle. And in the middle of an upcoming war, a human discovers that the war could actually be conjured by a power more perilous than the approaching enemy.