Frank and Joe Hardy investigate the mysterious disappearance of a champion race horse, a case that leads the teenage sleuths on a pursuit of a desperate and murderous villain.
In searching for a lost parrot who recites Shakespeare with a stutter, Jupiter Jones' firm of young detectives becomes involved with a missing masterpiece.
Fifteen-year old Fanny and her step-sister are drawn into mysterious occurences around their home in Scotland which seem to be connected to the unexplained disappearance of a young man in 1914.