John Stone is a fugitive.
I had started the sentence with his being "an agent with the DCS" but changed it because that statement holds two falsehoods. The first is that John Stone is not an agent, John Phillips is. The second is that the proper tense is 'was'. He is no longer a paid employee of any governmental organization; in fact, they would like to see him eliminated and pretend he never existed - under either name.
A quick explanation of the department acronym "DCS". It stands for the Defense Clandestine Service, "an arm of the Defense Intelligence Agency which conducts clandestine espionage, intelligence gathering activities and classified operations around the world to provide insights and answer national-level defense objectives for" the US government.
He worked for them for some time before everything went very wrong.
In his words, "I was an undercover agent for the United States - until I defected to East Germany. People thought I was a traitor but really I was still reporting to Washington as a double agent. When the Wall came down, I thought I was going home, maybe even get a medal. Instead, they tried to kill me. Someone with a secret to keep framed me for murder. It seemed I was a traitor. The only two people I could trust staged my death: Charlie Cabot, an American intelligence officer, and Danny Montreux, a French cop. They gave me a new life in a new name. I had become John Stone. So everything's fine except unless I can clear myself, I can never go home."
The murder he was taking the heat for was a frame job by a fellow DCS agent; while Phillips/Stone had been a double agent spying on the other side, someone in the DCS was spying for them and when the Iron Curtain began to fall and it looked like their truths might come out, that traitor needed to pin blame on someone else. Phillips/Stone was the chosen fall guy.
Stone is a man in his early 30s with longish dark brown hair, ruggedly handsome with a perpetually scruffy appearance. He is in pretty good physical shape which is very much needed as a good number of people are trying very hard to kill him. Some because they think he is a traitor, some because they know he isn't, and some because while he is out trying to prove his innocence, he runs into others in trouble and cannot walk away without trying to help.
As mentioned above, Charlies Cabot is an intelligence officer working as the cultural affairs attache in the US embassy in Paris and Danny Montreau is a colonel in the French Special Action Directorate. Another name mentioned in the numerous adventures Stone/Phillips has is Jacquie Decaux, a very attractive artist who also runs a garage specializing in fixing and refurbishing exotic cars and a woman who happens to be Stone's current landlord. All three will assist him in his efforts to prove his innocence as well as the times he gets involved in other people's troubles.