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.

Twins Danny and Josh reveal to neighbor Petty Potts that they have been on a quest to find marbles containing secret code and soon find themselves--as geckos--in her new secret laboratory within the very pink Princessland.

"Want to learn how to make and break top secret messages like a real spy? IF so, this is the book for you! Inside are more than 80 pages of tips, tricks, and practice exercises for writing and deciphering cryptic communications. You'll learn how to make your own invisible ink, hide your messages, create unbreakable ciphers, and craft your own decoder gadgets. You can use this manual to learn how to exchange top secret notes with friends"--Page [4]...

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.

After seven members of their family are kidnapped by an organization called the Vespers, Dan and Amy Cahill must race against time to track down an ancient map to pay as ransom to bring the hostages home.

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.

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.

The most dangerous secret in Amy and Dan's past is unveiled in Book 7 of the #1 New York Times bestselling series.

The hunt for 39 hidden Clues that lead to an unimaginable power have taken a heavy toll on fourteen-year-old Amy Cahill and her younger brother, Dan. They've just seen a woman die. They're wanted by the Indonesian police. They're trapped on an island with a man who knows too much about the death of their parents. And a tropical...