This book was first published in 1941. The above cover is from a 2013 release on Amazon (one reviewer complained about the typos). Find the first edition at your library if you can.
This is the first book of fiction written by MacInnes. It is placed in Germany in 1939 just before the invasion of Poland. Richard and Francis Myles are asked by a MI6 friend to check on one of their agents operating in Austria who may have been compromised. The Myles’ have taken their summer breaks from Oxford every year by traveling around Europe, so this year they would simply make a couple of extra stops.
But this is a spy novel set at the beginning of the war when nothing is so simple.
If you like the genera, I especially recommend this book, indeed, most of her books, because they are rich in detail that is almost impossible for modern writers to match. Helen married Gilbert Highet, the world’s leading classics scholar who both taught at Oxford and secretly worked for MI6. The two of them spent their summers traveling through Europe. Helen took notes on every place they visited which she later used to sprinkle her stories with all that detail. Highet was lured away to Columbia University in New York in 1937 where they lived the rest of their lives.
Don’t assume that Gilbert told his wife how agents operated. She had to watch what he did as they traveled and make logical conclusions. Violating the Official Secrets Act was a serious offense. I doubt he told her any more than that he gathered information.
The world was very different in 1939. After Germany annexed several neighbors, including Austria, their population was 80 million. Today it is 83 million without the other countries (they lost about 8 million of their population in the war). The UK with its Empire had 550 million; but only 47 million in the UK, today 68 million. The US was at 147 million, 331 million today. Nearly all countries were still largely rural and good paved roads were in the future, except for Germany.
This is considered one of her best books. Her second book, Assignment in Brittany, was so detailed that is was required reading for all agents preparing to jump into France.