After earning her doctorate in Marine Biology, Petra returns to her hometown of Ocracoke, North Carolina. She intends to spend one last summer with her best friend and adoptive family before starting a new job that will take her away from them for the next few years. Petra is obsessed with the ocean, so it's no surprise when she ignores the local legends about the vile creatures that inhabit the waters. After all, everyone knows the myths about the missing colony of Roanoke being taken by the creatures are only folk-tale. But after getting caught in a storm out on the water, Petra wakes in the middle of the ocean atop her surfboard, with only the memory of a long black tail in the water. With severe injuries, and another storm approaching, Petra will do anything to survive. Even if it means trusting the sea creature that emerges and promises to return her to safety.