Talking to Strange Men — Ruth Rendell

Safe houses and secret message drops, double crosses and defections - it sounds like the stuff of sophisticated espionage, but the agents and moles are schoolboys engaged in harmless play.

John Creevey doesn't know this. To him, the messages he painstakingly decodes are the communications of dangerous men, and as he comes face to face with the fact of his beloved wife Jennifer's defection, he begins to see a way to get back at the man she left him for.

And soon the boys are playing more than just a game....