The mermaid Lí Ban has long studied humans, fascinated by their culture and strange ways. But when she begins to have dreams in which she lived a human life, she decides she must have once lived in the surface world, in a past life. Determined to regain what she has lost, she makes a dangerous bargain, trading her tongue for legs.
But the bargain has a catch: she must win the heart of the man once she once saved from drowning. If he should ever wed another, she will lose her soul. Plagued by increasingly insistent dreams, Lí Ban realizes not only does she need to win a heart—she may have unfinished business from her past life.