Three years after the events in ''Nim's Island'', the island faces a new challenge. The operators of the ship Buccaneer have gotten permission to develop a pirate resort on the island, and Nim and her father pursue separate plans to stop them. Meanwhile, a city boy named Edmund, who has met Nim once before and decides to see her again, has run away from home to the island, inadvertently bringing Poaching with him. With her father, Jack Rusoe away on the mainland, Nim must learn to work with Edmund in order to save the island from the poachers.