J.R. Finn is an agent with the Department of Defense.
That's about as close to the identification of his organization as he can get because no one ever gave him more information or likely ever would. It is a case of 'if you have to ask, you don't need to know' and 'if you ask, you won't like the answer' and, finally, 'if I tell you, well, you know how the line goes'. So he works for them.
At least he did. Now he is retired so he doesn't officially work for them any longer except, of course, he never officially ever did and now that he is retired he doesn't anymore. Except when they offer another contract job, which he can always refuse for any reason but never does because this is the kind of work he does and he has never refused anything yet so why start now.
Finn is likely in his early forties and a happily single boat bum. We know his age because he has a daughter who has never met him who is in college in Florida and he helped make her when he was in the military so simple math gives us the probable answer. That and he, when meeting Mary Elizabeth (more on her in a moment), he is attracted to her (who wouldn't be except for maybe the snake tattoo) and then chastises himself for his interest with the self-admonition that he had a daughter just a couple years younger than her.
As just said, he was in the military and since he was very, very good at his job, which was taking out targets who needed removal, that meant he was over in the Middle East which did not do his marriage any good and when that relationship hit a very unpleasant end, there was really nothing to come back for so he stuck around doing what he did so well. Then then offered him a different job more or less doing the same job but in different locations and against different targets.
To Finn, whether he wore a uniform or not means nothing. He is still a soldier doing his job. Now, though, when he is not on assignment, he gets to spend his free time on the water and the only sand he has to deal with is on beaches. He owns the Island Girl sailboat and home and he goes wherever in the Caribbean he feels like it between jobs. He makes very good money working for them and has little to spend it on except for his boat (and paying for the college of the daughter who has never met him). The few times Finn might think about his life, he would undoubtedly say he liked it and has liked it for the twenty years he's done it and would likely keep doing it for many years. No reason to change, really.
And then he meets Mary Elizabeth. Now what her real name is sort of changes here and there, sometimes by her and sometimes not. She is a beautiful young woman who really would like a ride, well, anywhere from where she is (which is a small port in Puerto Rico) and he is heading somewhere already so Finn says sure. No hassles. No problems. Just grab some extra groceries and hit the seas. That's when a couple of guys getting out of a car decide she needs to come with them instead and she says no and proves it and from that moment on, life gets really interesting.