Jack inherits a fortune from his Uncle Mortimer with the requirement to deliver Scabby Doo to the Isle of the Hanna Barberians. Mortimer's ghost haunts Jack and Snuk on the ship trying to kill them. When they reach the island they find that Mortimer's butler Stewey was disguised as Mortimer's ghost to get the treasure for himself. To Jack's disappointment the treasure is dog biscuits.