A novel. Caroline MacLeod of Skye lived in the shadows of history. At Bletchley Park, she decoded Nazi military and naval Enigma messages and helped bring an end to the Second World War. Rising to the top of Britain's most secret intelligence agency, she went after and took down international criminals and global terrorists. Here is her story, or what she can reveal. It is a story of intrigues, of loves and lives lost, and four friends who struggled to make the world a better place.