Using their code-breaking skills, four middle-schoolers solve the mystery of the eccentric man who draws stick figures on his second-floor bedroom window.

Thirteen-year-old Ruby, a genius code-cracker and daring detective, gets an anonymous call setting a challenge that leads her to the headquarters of Spectrum, a highly secret anti-crime agency that needs her help to crack a code, but soon Ruby uncovers dastardly plans of the Fool's Gold Gang.

Liz the Whiz and her younger brother use codes, a chart, and a map of the backyard that matches a clock face to solve Zack's mystery. Includes a section with related activities.

Trying to solve coded messages leads the Critter Kids to a new member for their club.

Geronimo Stilton and his sister Thea search for a secret map hidden beneath a famous painting and soon uncover some amazing clues.

When Bertie the badger visits his grandfather at a retirement home for magicians, he learns that his grandfather's rabbit, Enigma, has disappeared along with everyone's magical things, and the reader is invited to help break a code to find the items hidden throughout the book. Includes a built-in decoder.

When the three cousins find some strange symbols carved in an old tree, they start learning about hobo code and in the process learn about the importance of kindness as well.

Charlie, Anna, and Emily must overcome their differences and work together to solve various puzzles leading to the secret treasure a famous female explorer left in Idlewood Manor before the adults do.

Sarah and Aidan begin to decipher a mysterious document that refers to the origins of Peter Pan and are suddenly pursued by a being that can take any form and will stop at nothing to get what it wants from them.

"SHINE's solar energy station is under threat from evil agency SHADOW. Special Agent EJ12 needs to lighten up. She must crack SHADOW's codes and overcome her fears to stop them before they turn the lights out on the SHINE network. That's the easy part. As EJ12, Emma Jacks can do anything. So why is she worried about going to her best friend's slumber party?"--