Can ancestral stories and tales of ocean mysteries save a peaceful country from war? Could the daughter of a dying race, together with resistance fighters and mine-seeking dolphins, dismantle a military machine? What strength might myths deliver when one nation's tyranny threatens to destroy the world?

Sixteen-year-old Livi, from the coastal country of Merritaine, must reach the Nocturne Isles. For legends say Nocturne holds healing springs—waters that could cure her mamá’s cancer. Passage to Nocturne is scarce, though, for Nocturne keeps more legends than that of healing waters.

Sirens—powerful, human-like, aquarian creatures—are said to haunt the waters of the Mar de Basilisk raging around Nocturne. Not to mention, Merritaine and Nocturne have been engaged in an unjust war, incited by Merritaine’s Admiral Eris Machai.

Livi’s closest friends, Célian and Jules, have been drafted as reconnaissance scouts—boys who work with trained dolphins to find and disarm sea mines left in the wake of the Admiral’s war. Though the ocean is littered with warships and arsenal, the seafarers fear Siren reports more than the threat of the war reigniting. For Sirens, legends say, can rend steel and flesh. And they can manipulate human thought.

Livi, though, dismisses Sirens as mythical. Monsters don’t take the form of sea legends. Monsters take the shape of Admiral Machai, of volatile sea mines, of cancer. Or so she believes until she and her friends learn the terrible motivation of the Admiral's war. Livi may be the only person able to stop him. But first she must learn to master her birthright: powers of influence, of strength, and of destruction.