Eye of the Needle by Ken Follett

His weapon is the stiletto, his codename: The Needle. He is Henry Faber, a coldly professional killer and Germany's most feared deep-cover agent in Britain. His task: to discover the Allies' plans for D-Day, and get them to Germany at all costs. It's a task he undertakes with customary relish and ruthlessness - until he encounters Storm Island, and a woman called Lucy . . . 'An absolutely terrific thriller, so pulse-pounding, so ingenious in its plotting and so frighteningly realistic that you simply cannot stop reading' Publishers' Weekly' A tense, marvellously detailed suspense thriller built on a solid foundation of fact' Sunday Times