Ariel doesn't want to kill men, like her sisters. Once she becomes of age, she will sing the legendary song of sirens, which will bring out her murderous instincts. If Ariel doesn't sing, she will face becoming an outcast, and death soon after. But until then, Ariel has a much more human heart and refuses to take innocent lives. In an attempt to be free from her destiny, she turns to her grandmother, who transforms her into a human.

Ariel soon meets Cassie and Carson who then get caught up in a quest to end all siren life, but at what cost? Ariel must make a decision that will change the world forever, even if she won't be there to see it.