Everyone who sees twenty-year-old Callie Linden is struck by her beauty, grace, and confidence. Her outspoken passion for the environment has led the local boys to dub her "The Goddess of Green Lake." But no one guesses that Callie is driven by a promise she's carried for fifteen years. When her mother ran away, leaving Callie, her two sisters, and their heartbroken father behind, she entrusted her oldest daughter with her secret. Only Callie knows that her mother believed herself to be a mermaid.
Now grown and studying marine biology at the University of Washington, Callie is determined not to fall prey to fantasies and romantic nonsense. But she has no way to know what fate has in store when she rescues an unusual orphaned baby sea otter. Her carefully constructed plans for a sensible life shatter when she finds herself drawn to Eel MacGregor, a struggling musician with secrets of his own.
Eel and Callie's shared fascination for the baby otter leads to deeper feelings between them. When they step outside the law to protect the otter, Callie is forced to confront the questions her mother left behind, while she and Eel must discover whether it's magic or madness that draws them together.