ciphers

When a mysterious letter written in code arrives at King's house for his human, Kayla, he follows the trail of the person who left it.

Siblings Dan and Amy Cahill have managed to avert one disaster recreation threatened by the man who calls himself the Outcast, but they have mere days to learn where the Outcast will strike next. The clues are pointing them toward a terrifying air disaster so they naturally think of the Hindenburg disaster, but how can that be the target when nobody in the present day travels by airship?.

Jax and Ethan must decode an ancient Greek cipher to uncover the location of two magical urns before the urns are used to remove all faith and love from the world.

Siblings Dan and Amy Cahill have managed to avert one disaster recreation threatened by the man who calls himself the Outcast, but they have mere days to learn where the Outcast will strike next. The clues are pointing them toward a disaster modeled after Hurricane Katrina.

Could the Mark Twain books hidden through Book Scavenger contain clues about the string of recent arson fires plaguing the city?.

When his math genius neighbor Ben manages to uncover the key to modern data encryption systems, Robert "Smiles" Smylie comes up with an idea to protect Ben from government agents out to steal the key. But while carrying out his plan, Smiles discovers that his own past may prove the greatest danger to both himself and Ben.

Explores the history of cryptography and codes, discussing a variety of different kinds of codes and ciphers, as well as how codes have been used by militaries throughout the world.

"An enigmatic message leads the Code Busters on a treasure hunt on creepy Alcatraz Island, where they must use their problem-solving skills to unravel the mystery"--Provided by publisher.

When a new book arrives at the library with a secret code written inside, Derek, with the help of his friends, follows the clues from one novel to the next and makes a discovery that may help him get past a terrible loss.

"Thirteen-year-old Dan Cahill and his older sister, Amy, are running out of time. An exiled Cahill known as the Outcast has already recreated three of history's worst disasters, and he's saved the worst for last. If Dan and Amy can't find and stop the Outcast fast, he will initiate a full-scale nuclear meltdown. But as Dan and Amy race around the world, they discover something horrifying. The Outcast's disasters are only a smokescreen to cover up his true plan, a diabolical revenge on the family that betrayed him. Soon Amy and Dan will have to confront a hard truth: Sometimes the only way to save the world is to sacrifice everything you love"--Back cover.