Princess Lira is siren royalty and most lethal of them all. With the hearts of seventeen princes in her collection, she is revered across the sea, until a twist of fate forces her to kill one of her own. As punishment, Lira is transformed into the one thing her people loathe most—a human. Robbed of her song, Lira has until the winter solstice to deliver Prince Elian's heart to the Sea Queen or remain a human forever.

The ocean is the only place Prince Elian calls home, despite being heir to the world's most powerful kingdom. Hunting sirens is more than an unsavory hobby—it's his calling. When he rescues a drowning woman in the ocean, she promises to help him find the key to destroying all sirens. But can he trust her? And just how many deals will Elian have to barter to eliminate mankind's greatest enemy?