The Tommy and Tuppence series is short, but very entertaining reads. In this book the now middle-aged married couple are bemoaning the fact that they are "too old" to be of any use to the British government during World War II, unlike when they were young during WWI. It is their son and daughter who now are actively fighting the Nazis while the useless Tommy and Tuppence sit home...she knitting for the troops, he putting in his time in his office. Then an old friend secretly recruits Tommy to help the government by locating to a coastal area and keeping a look out for fifth column activities and anyone who may be a spy. They arrange a story for Tuppence that Tommy is going to Scotland for the war office to do secret paperwork and there is no housing for Tuppence. Tuppence decides that rather than sit home alone she will go to the country to stay with an elderly aunt. One of the first people Tommy meets when he checks into his boarding house on the coast is a loud, pushy woman who is always talking about her three sons and the secret codes they write in their letters to her so that she always knows where they are and what kind of duties and actions they are involved in. Of course the woman is Tuppence herself, not to be left out of the war effort Tommy is involved in. Soon the intrigues mount and it becomes apparent that not everyone is who they profess to be, but when Tommy mysteriously disappears, it is up to Tuppence to find him and save his life and reveal the real Nazis spies.