Shayna's first surfing session of the summer is interrupted by the screams of a mother who has lost her little boy in the water. Without regard to her own safety, Shayna swims out, rescues the boy, but must escape the clutches of something far worse than she could have ever imagined - mermaids. Compelled to answer the sirens' call, the boys of Shayna's town are drawn to the sea, but when they return are afflicted by an unknown illness, a sickness which is draining them of their life force. Unable to tell anyone about the mermaids, Shayna and her friends are forced to solve the mystery before it's too late, and in doing so, Shayna will finally have to face the full force of her powers. Whether she's ready or not, she will have to face her true nature.