Doc Ford has a new mission for Sharks, Inc.: visit Sanibel Island’s Bone Field to find a wild orange tree that survived a disease that has been destroying Florida’s citrus. But Sharks, Inc. can’t find Doc's tree. Worse, the area is protected by a massive saltwater crocodile.

What they don't expect is meeting a recluse who is threatening to call the police if they trespass on her land. Reluctant to give up, the team learns the woman needs help. When she was young, she found King Calusa's grave and now she's being haunted.

To learn the truth, the kids return to the Bone Field. The thousand-pound crocodile is determined to protect its hatchlings. But crocs turn out to be the least of their worries when the trio discovers the woman’s neighbor is selling illegal reptiles—and he knows her secret about Calusa's medallion.