Ben Peters is an agent with British Intelligence.
Eventually he will be. He will think it is MI-6 but he will not be completely sure. His damnably annoying sometimes boss Pickering is not very forthcoming so he is never really sure who he is doing these crazy things for but he just cannot find it in himself to say no.
When we meet Peters for the first time, he is working for a bank in Paris on behalf of his American bosses. He is most definitely an American himself and had not really considered a move to Europe until around 1937 or so when an incident with his then-girlfriend had made him ponder a change and that is when the managers of the bank he worked for decided he was the man to send to help out in their Paris branch. He was ready to say no and his parents definitely were against the idea but then the chance to follow in Ernest Hemingway's footsteps and maybe do some writing instead of banking overwhelmed him and so he went.
Our introduction to him comes in early 1940 with the Germans heading towards Paris and things getting very exciting and Peters gets involved in a crazy plan that has no chance of working and he puts his mind and tenacity to it and surprises everyone including himself.
The series then jumps ahead a year and Peters is now in London, still being begged by his parents to come back to the States and not really wanting to leave the excitement of London during the Blitz and his writing is sort of taking off and that is when Pickering talks about doing a favor for a mysterious fellow. And so we then have the American Ben Peters working for someone British in some Intelligence group. Very hush hush. Very dangerous.
And then the third book takes another jump a couple of years and it is obvious that Peters has been doing the odd thing for them for some time and suddenly everything gets even dicier even though the War is just over but there are still lots to do and lots of danger doing it and Peters still cannot find it in him to take the safer route and just say no.