About the Book: In December 1941, after a bomb hits Deepdean School, girls May and Nuala are sent to stay with May’s sister Hazel at Bletchley Park. A code-breaker is shot, a top-secret message found, and Daisy’s brother Bertie is suspected. May, Nuala and friend Eric must unravel espionage, murder and secrets inside Britain’s wartime nerve-centre before time runs out