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

"Drop case or else danger for you and your family." This warning addressed to Fenton Hardy not only alarm 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...

The town's ten-year-old walking encyclopedia again solves ten neighborhood mysteries. The final solutions to the cases are at the back of the book, giving the reader a chance to compare his skill to that of Encyclopedia Brown.

America's Sherlock Holmes in sneakers continues his war on crime in ten more cases, the solutions to which are found in the back of the book.

Cam and her friend Eric chase the thief of Aunt Katie's wallet through an amusement park and find themselves involved in another case requiring their special detective skills.

Nancy and her friends help a woman search for her missing grandson.

America's Sherlock Holmes in sneakers continues his war on crime in ten more cases, the solutions to which are found in the back of the book.

A wounded homing pigeon carrying a mysterious message lands in Nancy's yard and she finds herself investigating the workings of a sanatorium.

While solving the mystery of an old man's disappearing fortune, Nancy ends a family feud and reveals the identity of an orphan of unknown parentage.

Nancy Drew tackles a mystery professional detectives failed to solve--finding a valuable centuries-old message in a hollow oak tree in Illinois.