Marina, a water-breather, has spent her seventeen years obeying the commands of her adoptive mother and empress of the sea, Cordelia. One night when Marina is making a soul collection for the empress, trouble arises. She makes a quick decision to protect a human, a forbidden act below the Surface. With powers other merfolk don't possess, Marina erases the young man's memory of the incident and leaves him to wake on a South Carolina beach. Beck, a teen with a devastating past, awakens in the sand near the edge of lapping waves with no memory of arriving there. Pieces of a horrific accident, and the face of a girl he's never met begin to plague his thoughts and dreams. Below the Surface, Marina hides her secret of having saved an air-breather. But when Cordelia discovers Marina's betrayal and accuses her of treachery, Marina is thrust into the human world with the task of killing Beck and collecting his soul. If Marina fails, she'll become one of Cordelia's many slaves. Will she kill him in order to save herself?