I really enjoyed this historical middle grade book set during WW2 at Bletchley Park. I have a little bit of background knowledge about the code-breaking that happened here, but didn't know a lot of the details so I was excited to see what this book had to offer. The book doesn't go into a huge amount of information about the war effort as it's narrated by 12-year-old Robyn and many secrets are kept from her by the adults. However, it does have many interesting details and I enjoyed hearing a war story from the perspective of a child/teenager and learning about how young people contributed to the war effort. The carrier pigeon element was also interesting to read about. I think this book would be a great read for a child who is learning about WW2 in school! The mystery theme of the book was intriguing although could be a little confusing at times. The book is fast paced, with chapters skipping months at a time so it covers the span of a few years. Overall, this was an enjoyable read and I rated it 4 stars. I would recommend it for children aged 8-13.