Researcher Lia mistakes a deadly Siren, Xavier, for a lonely merman and teaches him courtship songs and dances. He accepts her as his mate. When she flees, he kidnaps her, believing she betrayed him twice. She learns they met as children—he saved her, she forgot. He wants to keep her forever. She discovers she's pregnant. He lets her go. She captures him to force him to stay. Their pup is born. They marry. Xavier, once alone, finally has a family.
