After a summer of tagging sharks off the west coast of Florida, Sabina, Maribel, and Luke have a new assignment: searching for "survivor trees" that are resistant to the disease that is destroying the state's citrus trees. The search takes them to the remote mangrove islands of Sanibel Island, where they discover Spanish oranges, a grave, an immense saltwater crocodile, a reclusive woman who believes that the ghost of a dead king, beheaded by Spanish explorers, is haunting her, and her neighbor who is involved in the illegal reptile trade--and in their effort to protect the woman and her animals they are soon plunged into a struggle for survival.