The third spellbinding story about Sapphy and Conor's adventures in the powerful and dangerous underwater world of Ingo. A devastating flood has torn through the worlds of Air and Ingo, and now, deep in the ocean, a monster is stirring.

Mer legend says that only those with dual blood -- half Mer, half human -- can overcome the Kraken. Sapphy must return to the Deep, with the help of her friend the whale, and face this terrifying creature -- and her brother Conor and Mer friend Faro will not let her go alone!