Siblings Lizzie, 14, and Jakob, 19, who have grown up in England, are the children of an American mother and Polish father. Their father died years before. Now, with England fighting World War II, their mother, who worked for the American embassy in London, is presumed dead after being caught in Poland on embassy work as the German invasion there began. Irrepressible Lizzie refuses to believe their mother is dead. She evades the chaperone accompanying her to their grandmother in Cleveland and makes her way to their London apartment, where she finds documents her mother secreted under a floorboard. Cautious Jakob, annoyed by his sister’s rogue behavior and stressed by his responsibilities, reluctantly brings Lizzie back to his lodgings near Bletchley Park, where he, a math student at Cambridge, is now working on the secret Enigma codebreaking efforts. Alternating chapters focus on Lizzie’s efforts to prove their mother is alive, helped by two new friends, and Jakob’s work in Hut 6 on breaking the hold of Enigma on German messages. Slowly, their efforts converge, bringing them closer as they realize their mother was involved in helping Polish codebreakers—who contributed greatly to the work the British are doing at Bletchley—flee the Germans during the Polish invasion. This swiftly paced story is steeped in real as well as fictional intrigue.

A thrilling middle grade historical adventure from bestselling authors Ruta Sepetys and Steve Sheinkin

Remember, you are bound by the official secrets act...

It is the summer of 1940. The world is at war. These days, you don’t know who you can trust or who might be a secret spy…

Maths whizz Jakob Novis has been recruited to the secret codebreaking centre at Bletchley Park. As Jakob works to crack the Nazi’s Enigma cipher, his younger sister Lizzie is busy on an undercover mission of her own: to find their mother.

Filled with codes to decipher and mysteries to unravel, this is the unputdownable historical adventure that will have you on the edge of your seats.

'A thrilling World War II code-breaking adventure filled with ciphers, secrets, and spies.' Alan Gratz, New York Times bestselling author of Refugee

'Exquisite historical storytelling! I only wish I could read it again for the very first time.' Jennifer A. Nielsen, #1 New York Times Bestselling author of Iceberg