Serena, a mermaid, makes the ultimate sacrifice when she falls in love with Steve, giving up her magic and leaving her mer family forever to be with him. When he betrays and abandons her, she is condemned to die unless she can find a new love who will tell her he loves her within a year and a day. Devastated, she returns to the town where she came ashore to wait out her time, forbidden by the laws of magic to tell anyone of her origin or her predicament. Making new friends and working for Rose, an incorrigible elderly lady, the bittersweet realisation that this was what she had always longed for is eclipsed by the feelings she begins to share with Seth, Rose’s great nephew. A second chance seems possible… but Seth has little faith in love. Used to people leaving and trying to recover from a particularly toxic relationship, his kindness and generosity is reserved for others and not himself. His feelings for Serena bring up things that he’d rather not face, so he pushes them, and her, away. Tallie and Ethan, Seth’s closest friends and both in joyful relationships, try to help;
Tia, Serena’s mermaid sister, also offers a solution, though not the one that Serena longs for. Although Ethan realises the truth about Serena and her past, he feels powerless in the face of Seth’s distrust and as the days go by Serena sees her newfound hope washing away with the tide. Will Seth be able to say those three words before her time runs out and she too has to leave him?