The book is Wolves at the Door which tells the story of Virginia Hall, an American OSS agent and telegraph operator in France during World War II. Quite a bit of information on her can be found on Wikipedia.
If that whets your appetite, I can recommend the book to flesh out some of the details, including her training in Morse Code and radio operation.
Paul W0RW has a second biography on her, the more recently published (2019) A Woman of no Importance available to be borrowed from his Lending Library.
Although both books are available on Amazon, you may be interested in the other books contained within Paul's library.
Thanks for the info, Paul!
The image of Virginia Hall and one of her assistants, Edmund Labrat, is that of an oil painting by Jeffrey Bass, completed in 2006 titled "Les Marguerites Fleuriront ce Soir" (The Daisies Will Bloom at Night). An explanation of the painting's title can be found here.