Lighthouse keeper Tessa Lonike savors her solitude on Little Mer, an island off the coast of Maine, guarding her true identity as a mermaid. But when Tessa spots a man thrashing around in the ice cold waters during a storm, she must use her ability as a mermaid to pull him to shore.

A year later, when Kenneth Randall meets the woman who saved his life, he's determined not to let Tessa slip away. But when Tessa'a archaeologist ex-lover comes back to town with a clue to her heritage, she may be forced to leave her happiness behind.