For the past nine months, 15-year-old Nick Caden has written for an alternative webzine called Cool Ghoul Gazette. The online magazine covers strange paranormal events and occult-like activities. This job is a perfect fit for Nick, who solves crimes as a hobby. While his family is visiting Savannah, Ga., where Dad has a job interview, Nick decides to research a girl named Heidi May Laveau, who died years ago. A fisherman recently reported seeing her corpse washed ashore, but no one else has seen the body.
Life has been rocky for the Caden family. Dad’s unemployment has taken its toll on his marriage, and Nick fears his parents are planning to separate. While Mom and Dad go to a dinnertime job interview, Nick and his sister, Wendy, sneak out to an abandoned boathouse to work on Nick’s story. Wendy sits in a canoe and is suddenly abducted by what appears to be the zombie of Heidi May Laveau. Nick rushes to contact his parents and the police, and the search for Wendy begins.
While Officer McDonald and Nick’s parents search, Nick secretly follows a tip. A girl named Kat, who he saw sitting with friends at a bonfire upriver that evening, says she can help Nick find Wendy. Kat tells him about the Gullah people, descendants of slaves who know a lot about zombies and voodoo. She says there’s a Gullah woman named Annie he needs to visit on a nearby island. Then Nick starts getting text messages from Wendy’s kidnapper, saying he wants his life back, and Nick is the only one who can help him.
Nick doesn’t know anyone in town, and he wonders who could know his family is there. He talks to Ms. Bryant, the kind, high-powered real estate agent who interviewed Dad for the job. Nick also speaks briefly to her haughty aide, Matt. Nick questions Officer McDonald and his assistant, Dirk. Although he enjoys Kat’s company, he wonders how she knows so much about his sister’s case. As his parents continue to argue, Nick follows leads. He finds evidence at a condo owned by McDonald indicating that someone followed Nick’s family from Kansas to Georgia. McDonald catches Nick at the condo and claims he’s renting it out to someone he hasn’t actually met.
Kat stays in the boat, but drops off Nick on the island near to Annie. When Nick asks questions, Annie talks more about God than about voodoo. Nick sees the dead Heidi May Laveau once more and follows her into the woods. There, he discovers Matt, the real estate assistant, has been playing the part of Heidi May. Matt has been pretending to be the dead girl because he is an aspiring actor, and the kidnapper had convinced him to take this as an acting gig. Matt falls into a pit, and it’s implied that he dies of a broken neck.
Kat remains near the boat until the kidnapper finds her and takes her to his hiding place, where he is also keeping Wendy. Nick finds Kat and Wendy with the real kidnapper. He’s a man named Gabrovski, whom Nick helped put away in a previous case. The man tries to drown Nick in the dead low tide while burying Kat and Wendy alive. Nick holds his breath long enough to fake his own death. Then Officer McDonald, whom Nick had tipped off, arrives with Nick’s parents and surprises Gabrovski. Gabrovski gets away, forcing Nick and his family to enter witness protection.