Annie and her best friend Sam like nothing better than going “swamping” – searching for treasures in the big, beautiful swamp by Annie’s home. They’ve discovered many cherished items in the swamp, including a small plastic bell, an earring with a red stone in its centre, and a fishing lure that looks like a worm. But when an old rowboat drifts ashore during a strong wind, Annie and Sam not only discover their biggest treasure ever, but they also uncover something truly special: a shiny golden locket stuck between the boards of the old boat.
Annie, Sam and their friends embark on a quest to return the locket to its owner. But their mission is hampered by a number of obstacles, including finding the location of Spirit Cove, the appearance of mysterious notes on Annie’s windowsill, their encounters with Miss Matilda and the Hermit, and the search for a lost Chest of Treasures. The difficulties continue to grow when Annie’s slipping grades at school prompt her parents to restrict her swamping time. But how can Annie focus on a boring history project when adventure calls? It is only when she discovers the true identity of the owner of the locket that Annie realizes that history can be interesting after all and that each of us has a valuable story to share.