The Mystery Inc. gang has no idea that their class trip will include a visit from the ghostly Captain Barnacle. And when Shaggy, Scooby-Doo, Daphne, and Fred all become seasick, it's up to Velma to try to track down the passengers' stolen backpacks and the Hex Girls' musical gear! Could the mysterious dust on tarps and the deck floor be a clue? Join Velma and the Hex Girls as they work together to solve another spooky case in this all-new, all-hands-on-deck Mystery Inc. Picture Book mystery.