At the end of Siren's Storm, the Sirens were defeated, and now the town of Walfang is once again a peaceful beach community.

Or is it? Gretchen and Will are still haunted by the memories of the night the Sirens were destroyed - Gretchen because she can't remember what happened and Will because he doesn't know how to tell Gretchen what he saw. He doesn't even understand what he saw, but he does know now that Gretchen is more than what she seems, more than a human girl. And at the same time, he is more in love with her than ever.

Gretchen knows there's something wrong, too. She feels like an alien in her own body, but she doesn't know why. And she feels a presence stalking her at every turn. Have the Sirens returned to Walfang? Or has some other force come to claim her?