12-year-old Kela never imagined “I hate you” would be her last words to her mother, and after her death, Kela would do anything to take it back. Powerless to change the past, she finds solace in jewelry-making and the sea. While searching for sea glass, Kela salvages a mysterious box containing a beautiful hair comb. When she touches it, a magical connection opens to a dangerous mermaid named Ophidia.

Bound by rules of magic, Ophidia offers Kela a wish in exchange for her comb’s return. With only three days to return it, Kela accepts and wishes her mother back from the dead. At first, Kela is overjoyed to have her mother back but soon realizes something is not right. Before Kela can help her mother or keep her end of the bargain with Ophidia, the comb is stolen.