* New York Times Bestseller
* Five starred reviews
* #1 Indie Next Pick
* ALA Notable Book

This thrilling WWII mystery--a collaboration between award-winning and bestselling authors Ruta Sepetys and Steve Sheinkin--is now in paperback!

Exclusive Barnes & Noble Edition Content: Author Q&A, A Guide to Secret Codes, A Note on History, Discussion Questions, Deleted Scenes, Timeline, and B&N Exclusive Ciphers!

Remember, you are bound by the Official Secrets Act...

Summer, 1940. Nineteen-year-old Jakob Novis and his quirky younger sister, Lizzie, share a love of riddles and puzzles. And now they're living inside of one. The quarrelsome siblings find themselves amid one of the greatest secrets of World War II--Britain's eccentric codebreaking factory at Bletchley Park. As Jakob joins Bletchley's top minds to crack the Nazi's Enigma cipher, fourteen-year-old Lizzie embarks on a mission to solve the mysterious disappearance of their mother.

The Battle of Britain rages and Hitler's invasion creeps closer. And at the same time, baffling messages and codes arrive on their doorstep while a menacing inspector lurks outside the gates of the Bletchley mansion. Are the messages truly for them, or are they a trap? Could the riddles of Enigma and their mother's disappearance be somehow connected? Jakob and Lizzie must find a way to work together as they race to decipher clues that unravel a shocking puzzle that presents the ultimate challenge: How long must a secret be kept?

Binding Type: Paperback
Publisher: Viking Books for Young Readers
Published: 10/28/2025
ISBN: 9780593527559
Pages: 416
Award: Golden Kite - Honor Book
Accelerated Reader Quiz #/Name: 551711 / Bletchley Riddle
Reading Level: 4.1 / Interest Level: Middle Grade Plus / Point Value: 10