Twin sisters Georgie and Gem care about the environment and are deeply ashamed of their stepfather Geoffrey, who sells detergents made of bad chemicals that fill the sea with toxic slime.
The twins try to convince Geoffrey to get another job, but he refuses. ‘ZOOM’ is the world’s best-selling cleaning product, and Geoffrey loves being a superstar salesman – even though his boss, Zachary Zigstack, only pays him peanuts.
Together with a tribe of grubby goblins called the Slapstyx, Zigstack has hatched an ingenious plan to make sure everyone buys his dastardly detergent. He has promised the Slapstyx a mountain of gold, which he has yet to deliver.
Georgie and Gem can leave their bodies at will and fly around in an astral vehicle they call their ‘dreambody’. This ‘dreamwalking’ enables them to travel to other dimensions and meet the creatures that live there. One night they dreamwalk to the goblin dimension and rumble Zigstack’s pact with the Slapstyx. The goblins threaten to kill them if they tell anyone about it.
The twins make friends with a mermaid called Eltra whose tribe – known as the Delphinae – look after the dolphins. The ZOOM overload in the sea has created toxic plankton-based monsters called Sloyds who are out to destroy all the other sea creatures. Eltra begs the twins for help.
Though they are terrified of the Slapstyx, Georgie and Gem promise Eltra they will try and stop them working for Zigstack. But can they do it before the world’s oceans are turned into toxic plankton soup?
More to the point, can they do it before the goblins put them out of action for good?