"Drop case or else danger for you and your family." This warning addressed to Fenton Hardy not only alarms the famous investigator and his detective sons, but also puzzles them, because Mr. Hardy is working on more than one case. Which one prompted the threat? When more ominous warnings follow, Frank and Joe suspect there is a link between the counterfeiting case they are investigating and a secret case their father cannot discuss since it involves...

In 1871 Wisconsin, thirteen-year-old Georgia sets out to find her sister Agatha, presumed dead when remains are found wearing the dress she was last seen in, and before the end of the year gains fame as a sharpshooter and foiler of counterfeiters.

While celebrating his birthday with his family, Geronimo realizes someone has replaced all of his money with counterfeit bills and sets out to find the thieves.

Thirteen-year-old Sammy meets a mysterious man who dies of a heart attack after telling her to get rid of the large amount of money he is carrying, leading her to investigate who the man was and how he came to be carrying so much cash.

When they uncover a conspiracy against America and its fundamental freedoms, the Kidd children, accompanied by their great uncle, crisscross the country in a race to prove that a newly-discovered copy of the Bill of Rights is a forgery.