Our Friends In Berlin by Anthony Quinn

Set in Blitz-battered London, this wartime espionage thriller follows an undercover British agent who infiltrates a ring of Nazi sympathizers by posing as their conduit to Germany, drawing a cautious young woman into his operation as a courier while hiding his true allegiance. As air raids, paranoia, and MI5 machinations intensify, desire and duty collide, betrayals mount, and a high-stakes sting tightens, testing loyalties and exposing the moral compromises demanded by survival in a city under siege.