A handbook for the budding cryptographer including codes and ciphers, invisible inks, concealment techniques, spy stories and some history.

National Bestseller

NPR Best Book of the Year

"Not all superheroes wear capes, and Elizebeth Smith Friedman should be the subject of a future Wonder Woman movie." —The New York Times

Joining the ranks of Hidden Figures and In the Garden of Beasts, the incredible true story of the greatest codebreaking duo that ever lived, an American woman and her husband who invented

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A clue takes Amy and Dan Cahill to Egypt, where they investigate the origins of the rivalry between the Tomas and Ekaterina branches of their family and try to figure out if they can trust a message from their dead grandmother Grace.

"Teaches readers how to make secret codes and messages through clear steps, simple supplies, and helpful tips."--

An intruder at mad scientist's Petty Potts' house interrupts her latest experiment, trying REPTOSWITCH on twins Josh and Danny, and when they return home they find a package that sends them on a mysterious quest.

Eleven-year-old Fish, seeking a way to help his family financially, becomes a reluctant cabin boy on a pirate ship, where he soon makes friends--and enemies--and is asked to help decipher clues that might lead to a legendary treasure.

When Amy and Dan learn the truth about the Madrigals and Grace Cahill's alternate will, these discoveries lead to the revelation of a secret about their family and a showdown with the man in black who has been following them.

When Amy and Dan Cahill trace the footsteps of a formidable military leader from the Cahill bloodline, they uncover a devastating secret about the family that changes everything.

Dan and Amy Cahill are given the choice of receiving a million dollars or uncovering the thirty-nine clues hidden around the world that will lead to the source of the family's power, but by taking on the clues, they end up in a dangerous race against their own family.

The third book in the CAHILLS VS. VESPERS series, the follow up to the worldwide bestseller THE 39 CLUES.

The Vespers have crossed a line. Amy and Dan were devastated when the Vespers kidnapped seven Cahills around the world, holding them hostage until Amy and Dan delivered an impossible ransom. But at least the hostages were Cahills - members of the world's most powerful family, trained to face all odds.Now the Vespers have gone too far. They've...