Stephen Wheatley looks back in old age, and from a different country, on the wartime summer when everything changed for him, in the quiet suburb where he lived with his family. The 'spies' of the title are the German agents whom boyish imagination sees round every corner, but the term applies just as well to Stephen himself and his best (if not only) friend, Keith Hayward, once they get it into their heads to watch people's movements.