The pace and the action of this book would have normally made it a four star read. Then the end happened. It was such an unbelievable sequence that I had to take a star away. This series seems to have an unbelievable element in every novel but this novel took the cake.
The meticulous research the author did is obvious. There were a few points where the story pacing suffered from the dreaded information drop. I did not find it took away too much from the story. The history of spies, particularly female spies, in WWII is a pretty fascinating topic. The end where the British master plan is revealed, is particularly fascinating. I'm not on a mission to do some extensive research on people like Henri Dericourt, Vera Atkins, and Noor-un-Nisa Inayat Khan.
While some have suggested this book could be read as a stand-alone novel, I would highly recommend starting from the beginning.