The gang decide to go traveling in the Mystery Machine, seeking fun and adventure during what could possibly be their last summer break together. However, havoc-wreaking monsters seem to be drawn to them, appearing almost every stop of the way.
At a seafood restaurant, the ghost of a legendary pirate, Half-Beard, has been scaring away the customers. Captain Cutler joins the gang on a treasure hunt at Double-Cross Cove where Half-Beard's treasure is supposedly buried.