January 1944. An untouchable German reconnaissance aircraft threatens to reveal the Allied preparations for D-Day; will the RAF stand any chance of dealing with it? Just months to go before D-Day and the Germans are routinely sending a reconnaissance aircraft at stratospheric height over southern England; this time the stripped-down Spitfires and Mosquitos stand no chance of intercepting it. With the preparations for the invasion of France - and the ultimate end of the war - now in jeopardy, ace night-fighter pilot Flight Lieutenant Alec Keats joins a small team that is struggling to get Britain's only hope into a state where it can bring the German machine to earth. Keats throws himself into the technical problems that need to be resolved if the team are to stand any chance of success; his only distraction being the enigmatic WAAF who seems to be unusually close to the unit's commanding officer...