The Ghost at Skeleton Rock — Franklin W. Dixon

A cryptic message from their famous detective father and a note concealed in a ventriloquist's dummy lead Frank and Joe Hardy on a dangerous search to the tropical islands in the Caribbean. There the teenage detectives are constantly beset by vicious henchmen of a criminal mastermind. Danger stalks the boys' every move, once in an isolated sugar mill, another time in a shark-infested sea. But when Frank and Joe come face to face with the ghost at Skeleton Rock, it will be as much of a surprise to the reader as it was to the young detectives themselves.