It is 1955 and post-war Berlin is crawling with subterfuge. East eyes West, and the West is eavesdropping on Soviet communications through Operation Gold, a daring technological collaboration between Britain and America which is already straining with distrust.

That freezing winter a young British Post Office technician, Leonard Marnham, begins his dizzying descent into ever-deeper echelons of electronic surveillance beneath the surface of Berlin. At the same time he is lovingly initiated by a beautiful young German called Maria. He feels he is throwing away his life - and the abandonment is delicious. As these two worlds - personal and professional - claim Leonard, he senses that his life is about to change.