To end the curse they must face the truth.

When Allie wakes up alone in an emergency room in Hawaii, she faces difficult questions. A boat owner found her half-conscious, naked and alone at a deserted dock. Where is her ID? What is the strange disease that threatens to kill her? Does she have a family?

Meanwhile, thousands of miles away in Arizona, her twin sister, Alysa, lives. Alysa struggles to rebuild her life after being in a coma for years. Both sense the other twin needs help but neither knows how to answer the call…or if they are deluding themselves.

When they meet, it sets off a cataclysmic reaction. In this riveting series conclusion, Allie and Alysa must face the creature that has stalked them since birth. Succeed and they might live lives fit for mermaid queens—fail and all they know will drown in the deepest darkness.