A mermaid named Harper is warned by a fellow mermaid about the danger of trusting humans, citing a past punishment. Despite the warning and the law, Harper insists on returning to land for the man she loves, Rhett. Her companion reluctantly lets her go, reminding her she must soak in water daily or risk turning into foam if exposed. Harper arrives back only to learn from public news that Rhett, a powerful CEO, is now rumored to be engaged to a rising pop star, Vivian.