Ava, a sixteen-year-old orphan, longs for a family of her own. When she’s placed for adoption with Matthew and Hannah Castle, she wants to believe it’s forever. But the morning after she arrives at the Castle home in Salem, Massachusetts, she notices mysterious changes in her body, including glimmering tattoos on her skin and scales on her legs. These strange occurrences worry her that just as soon as this new life is in her grasp, that she’ll just as quickly lose it all.
As she unravels the mystery of her true identity, her past, and that she’s mermaid royalty, Ava must decide if she wants to stay on land or return to her kingdom in the sea. Amid these changes and revelations, Ava goes on her first date, learns that she has magical powers, and gets a startling confession from her best friend.
After an attack by her enemy, Ava learns that someone near to her heart has betrayed her.