The Hardy Boys are super excited when their friend Jason Wang wins the "Talk Like a Pirate Contest" at Bayport's annual Pirate Palooza. Jason's prize is a map to the legendary pirate, Captain Scurvydog's buried treasure. Expert detectives Frank and Joe offer to help him find it.

But the next day, Jason tells the brothers that he won't be doing any treasure hunting. He says the ghost of Captain Scurvydog has been haunting him; his parrot is singing pirate songs he's never been taught, pirate coins appeared on his windowsill, and there's a mysterious note in a bottle warning Jason to stay away from buried treasure. To Jason, the message is clear: stay away from Captain Scurvydog's booty Frank and Joe don't believe in ghosts. They're sure someone is tricking Jason so they can dig up the buried treasure themselves. The only question is, who?