This classic starts off with a bang. Henry Faber has two identities. The one in London is a quiet man who keeps to himself on the top floor of a house being sublet by a widow. She takes a fancy to him one evening and with her duplicate key happens to walk in on him just as he's getting the transmitter out to send messages back to the Abwehr. He has to kill her.
Faber (Called Die Nadel for his use of the stiletto) is an elite German spy, inserted into England before the war and now embarked on the most important task of his career, trying to determine the most likely landing point of the Allied invasion.
Follett shifts viewpoints between Faber and the British counter-intelligence team (the trick they used to determine Faber’s identity was quite clever,) and Hitler’s general staff The book is all about deception: Faber’s, the turning of German agents into double agents, and the Ghost Army.
Pillars of the Earth was amazingly good, this one not quite so, but well worth the time.