Dixon, Franklin W

A "monster" who terrorizes Bayport and a girl who runs away to join a cult are the subjects of the Hardy boys' sleuthing.

When their detective father asks them to play burglar in order to protect a client's valuable invention from thieves, the Hardy boys find themselves involved in a large and dangerous conspiracy.

The Hardy boys embark on another puzzling mystery when they try to discover who is stealing rare collections of ancient pirate treasure and smuggling them out of the United States.

Frank and Joe uncover a plot to steal a vital top-secret instrument of the space program.

After a dying criminal confesses that his loot has been stashed "in the tower", the Hardy boys make an astonishing discovery.

In the Northwest Territories of Canada, the Hardy brothers and Chet Morton help to recover a stolen Viking relic.

Joe and Frank Hardy investigate the disappearance of girl from an amusement park ride.