A lone German bomber crosses the East Coast of Britain on a moonless night in the long, hot summer of 1940 and drops his bomb over Cambridge's railyards. 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. Detective Inspector Eden Brooke is first on the scene and discovers the body of an elderly woman, Nora Wylde, beside her shattered bed in a terraced house on Earl Street, two fingers on her left hand severed, in what looks like a brutal attempt by looters to steal her rings. But when the next day her teenage granddaughter, Peggy, a repair worker at Marshall airfield, is reported missing, Brooke realises there is more to the situation than meets the eye.