Lira is a feared siren, known as the “Prince Killer,” who collects the hearts of human princes for her mother, the Sea Queen. After disobeying her, she is turned into a human as punishment.
She is then forced to kill Prince Elian, a pirate who hunts sirens. However, their meeting changes everything: instead of killing each other, they form an alliance to find a magical artifact capable of defeating the Sea Queen.
During their journey, they discover that their peoples are not simply enemies and begin to question their beliefs and loyalties.