Mermaids are going missing from sixteen-year-old Maya’s pod—including her best friend. Maya just wants to swallow her grief and pass her siren trial so she can become an ambassador. The trial tests every young mermaid’s immunity to siren enchantment, which they must prove by enduring siren song without joining in at the dangerous southeastern boundary. Failure spells banishment. When a human hunter attacks her swim partner during the trial, Maya’s song bursts out, repelling the attacker and saving her partner. Maya is sure the hunters are abducting mermaids. But the Mermaid Council blames sirens. 

Frustrated by her pod’s failure to recover the missing girls, Maya seeks help from her sister’s secret human boyfriend and his charming cousin—and from the sirens, including the cold but captivating Kai, whose song Maya can’t stop humming. Risking enchantment, capture, and banishment, Maya races to master her song, find the hunters, and rescue the missing mermaids, before any more disappear. As the attacks escalate, Maya must choose between retreating to the safety of her pod or embracing the sirens’ dangerous freedom. And that means deciding whether her song is a curse to be freed from, or a gift worth fighting for.