An angry, grieving seventeen-year-old musician facing expulsion from her prestigious Brooklyn private school travels to Paris to complete a school assignment and uncovers a diary written during the French revolution by a young actress attempting to help a tortured, imprisoned little boy--Louis Charles, the lost king of France.

Uncovering an ancient evil, Serafina, a mermaid of the Mediterranean Sea, searches for five other mermaid heroines who are scattered across the six seas, to save their hidden world.

A young woman in nineteenth-century New York City must struggle against gender and class boundaries when her father is found dead of a supposed suicide, and she believes there is more than meets the eye, so in order to uncover the truth she will have to decide how much she is willing to risk and lose.

"Astrid must confront her ancestor, Orfeo, the evil force behind the rise of the monster Abbadon, while Sera and her Black Fins train goblin troops for battle against her uncle Vallerio's death riders"--

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...