This story takes place in Bletchley Park at the start of the second world war. The main character is a twelve year old girl named Robyn who lives in a cottage that belongs to the Bletchley Park estate. She is able to live there because her father is a chauffeur employed by the people who own the estate. Robyn wants to work with her father when she leaves school because she knows she will be happy working with cars. She is also looking forward to her father giving her driving lessons soon after her thirteenth birthday.
Then just before her birthday, life on the Bletchley Park estate starts to change. There are suddenly more people living there and Robyn thinks there is something very suspicious going on especially when she is called over to the main house and she has to sign an official secrets form. She is also given the task of helping to look after the carrier pigeons. With the help of two friends, Mary and Ned, she sets out to find out exactly what is going on.
Then just before her birthday, life on the Bletchley Park estate starts to change. There are suddenly more people living there and Robyn thinks there is something very suspicious going on especially when she is called over to the main house and she has to sign an official secrets form. She is also given the task of helping to look after the carrier pigeons. With the help of two friends, Mary and Ned, she sets out to find out exactly what is going on.