Nate the Great investigates the disappearance of a homemade pillowcase belonging to Rosamond's cat Big Hex.

When George takes a delivery job for a local pharmacy, three customers fall prey to lethal poisons that are substituted for medicine, and Nancy must solve the case before George is named a prime suspect

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

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.

Readers can read the story and try to figure out the clues along with Marie and her pals, and can find out if they solved the mystery correctly by checking their answers at the back of the book.

While visiting Wallis's castle, Dink and his friends investigate strange noises that lead them to a dangerous secret.

When Kristy, Claudia, Mary Anne, and Stacey, the members of the Baby-sitters Club, each receive mysterious calls while they are working, they decide to find out who is responsible.

It's Cam and Eric's first day of fith grade, and both are looking forward to meeting their new teacher. But when they arrive at school, their teacher is taken away by the police!

The Aldens' dog, Watch, comes across a mysterious box with a note inside, a box that is part of a game called Geocaching. Henry, Jessie, Violet, and Benny join the game but soon suspect one of the members of the geocaching club is a thief.

When her pony, Sundance, goes missing, Princess Ellie blames a mysterious stranger for the disappearance, so Ellie and her best friend Kate must track down the mystery person and get Sundance back before it is too late.