lone German bomber crosses the East coast of Britain on a moonless night in the long hot summer of 1940. The pilot picks up the silver thread of a river and following it to his target, drops his bomb over Cambridge's rail yards. The shell falls short of its mark, and lands in a maze-like neighbourhood of terraced streets on the edge of the city's medieval centre. D I Eden Brooke is first on the scene and discovers the body of an elderly woman, Nora Wylde, beside her shattered bed in a terrace house on Elm Street, two fingers on her left hand severed, in what looks like a brutal attempt by looters to steal her rings. When the next day Nora's teenage granddaughter, Peggy, a munitions worker at Marshall's Airfield, is reported missing, Brooke realises there is more to the situation that meets the eye.