Nancy and her friends are on a fun-filled trip to the coast of Maine. But when they find out that the historic town lighthouse might be haunted, the girls are spooked! And when they find mysterious clues that seem to lead them on a treasure hunt, Nancy knows she has a mystery on her hands. Who wrote the clues? And where could they lead? Maybe this lighthouse really is haunted like everyone thinks. One thing's for sure—it's up to Nancy to shed some light on this case before they are all left in the dark!