During the 100th birthday celebration of Emerald Cove, 12-year-olds Dave, Freddy and Jonathan stumble upon clues that raise some puzzling questions about the strange disappearance of the lighthouse keeper 30 years ago. Determined to solve the mystery, the three boys soon find themselves on the adventure of a lifetime. Pursued by four bumbling villains, the boys are swept into a whirlwind of adventure and discovery in a madcap race to solve the mystery. Will Freddy, Jonathan and Dave find out what's at the end of the secret passage? Will they fit all the pieces of the puzzle together? And will they get the bad guys?