Twelve-year-old Robyn has grown up at Bletchley Park and when she's not been at school she has enjoyed working with her father in the garages, but when the war starts their lives change.

Robyn is told not to leave the grounds of the park and is required to look after the carrier pigeons that take messages to the Allies. It's important work and she has to sign the Official Secrets Act.

Robyn has mixed feelings about her role. She becomes fascinated by the birds, but soon suspects that there are sinister goings on and she enlists her friends Mary and Ned to help her uncover the enemy in their midst!

It's a well paced adventure with great characters and seamlessly weaves in fascinating facts about the war effort. It is aimed at readers aged 9-12.