As Serafina uncovers more clues about the talismans, Neela ventures into a sea dragon's nest, and Ling learns the identity of their foe.

Once a lost and confused princess, Serafina is now a confident leader of the Black Fin Resistance (BFR). While she works on sabotaging her enemy and enlisting allies for battle, her friends face challenges of their own. Ling is in the hold of Rafe Mfeme's giant trawler, on her way to a prison camp. Becca meets up with Astrid and learns why the Ondalinian mermaid is always so angry: she is hiding a shameful secret. Ava can't return home, because death...

At the end of Dark Tide, Book 3 in the Waterfire Saga, Astrid leaves her mermaid friends to confront her ancestor, Orfeo, the evil force behind the rise of the monster Abbadon. Orfeo possesses one of the six talismans that the merls need in order to keep the monster locked up forever. But without the ability to songcast, how will Astrid be able to defeat the most powerful mage in history? Meanwhile, Serafina and her Black Fins train goblin troops...