Frank and Joe are invited to join a charter flight which passes over the Bermuda Triangle.

Nancy is held for psychiatric observation when she tells the police an unbelievable story.

Joe awakens in a Hong Kong hospital and is led to believe that he has been comatose for a year and his father and brother are dead.

While in New Orleans for Mardi Gras, Frank and Joe's wallets are stolen; Nancy works under cover as a magician.

The brothers find a dead man in a coffin in their hotel room.

The boys go under cover at a New England college where three coeds have been kidnapped.

Joe Hardy is still haunted by memories of his dead fiancee, but has to focus his mind on the case when Jocco's girlfriend overhears him talking to the police on the phone. Meanwhile, Frank Hardy tries to help Joe by going undercover too, but Jocco finds out and traps Frank in a shark-infested area.

Frank and Joe Hardy journey from the South of France to the Caribbean to find a girl who disappeared while hunting for pirate treasure.