Bletchley Park was a well-kept secret during World War II, operating under the code name Station X. The critical work of code-cracking Nazi missives that went on behind its closed doors could determine a victory or loss against Hitler's army. Amidst the brilliant cryptographers, flamboyant debutantes, and absent-minded professors working there, it was teenaged girls who kept Station X running. Some could do advanced math, while others spoke a second language. They ran the unwieldy bombe machines, made sense of wireless sound waves, and sorted the decoded messages. They were expected to excel in their fields and most importantly: know how to keep a secret.

Introduction -- 1939-1945: War and Y -- 1940: Secrets, secrets, and more secrets -- 1941: Ciphers, spies, and a mysterious summons -- 1942: Bombes and codebooks -- 1943: Slogging, grinding war work -- 1944: D-Day and its secret helpers -- 1945: War's end and the years after.