When Serafina, a mermaid of the Mediterranean Sea, awakens on the morning of her betrothal, her biggest worry should be winning the love of handsome Prince Mahdi. And yet Sera finds herself haunted by strange dreams that foretell the return of an ancient evil. Her dark premonitions are confirmed when an assassin's arrow poisons Sera's mother. Now, Serafina must embark on a quest to find the assassin's master and prevent a war between the Mer nations.