Adderly is an agent with the ISI.
That acronym stands for "International Security and Intelligence" which tells quite a bit about what it is and what it does but does not lend any help to telling us what country it is a part of. My money is on its being American because many of the adventures take place in the States and Adderly flashes his badge enough to clearly show it has some authority. So I list it as American but if someone were to argue, I would put up no real defense.
Running the ISI, or at least the operations end of things, is Major Jonathan B. Clack, a man who clearly had been an operative himself at one point considering how well he knows the field and what it takes to survive and succeed in it. The rank of Major seems a bit low for someone in his authority but it could be he left the military to join the ISI.
Adderly was for many years the ISI's top agent and scored a considerable number of successes for it, and amassed a good number of enemy agents out for his scalp along the way. He is in his mid-30's when we meet him so it would not be unreasonable to think he had been an operative for around 10 years.
Then came the mission that would change his life and career forever. Caught by an agent for the other side, a particularly nasty piece of work named Victor Barinov, Adderly refused to talk when interrogated so Barinov used a medieval mace on Adderly's left hand, ruining it for life and making so unpleasant to look at that Adderly would keep it in a black leather glove and usually in a pocket.
With his life in the field gone, even after recuperation, Adderly was given a transfer to a department inside the agency with the nebulous title of Miscellaneous Affairs. If you were to ask, and quite a few people do in the adventures we have of Adderly, "What is 'Miscellaneous Affairs'?", Adderly would likely have a different answer for each query, none of them being all that flattery. My favorite is "Your tax dollars at work".
To say that Adderly was unhappy with the transfer would be putting it very mildly. He abhors his demotion and looks for any way he can to prove that even with his disability he can handle himself back in the action. Major Clack is alternately amused by and irritated by his constant efforts to achieve reinstatement. Meanwhile, Adderly is given a new menial assignment every week.
The amusing things about these assignments is that Adderly seems to find some way to make them turn out to be something important. In the first adventure we have of him, Adderly is given the posh job of heading up security for a Senator's daughter's wedding, but instead of just playing it easy, Adderly determines the groom-to-be is an international assassin in hiding. The other missions are in a similar manner of looking like one thing which really being something else.
Plaguing Adderly's every day at work is his inane, obsequious, mealy little boss, Melville Greenspan, a fellow who would find inventorying paperclips a successful day's work. Adderly is greatly vexed to have to work for such a person and Greenspan is greatly vexed that his sole agent is constantly causing trouble.
The lone shining star in Adderly's professional existence is Mona, the funny and amusing secretary for Greenspan who is not only quite intelligence herself (far too smart to deserve working in the basement like she does) who constantly comes up with data that Adderly needs to crack a case. If Mona does not know it or know how to get it, she is always earning favors for other secretaries in other departments who can deliver the scoop. If someone somewhere in the headquarters needs a gerbil or a dog or a cat looked after for a while, Mona is the one to call and in return, she is owed a favor.
Adderly has, understandably, a major chip on his shoulder. He knows he can still do his job and wants to do so badly but no one will listen. In the meantime, he is nevertheless proving it with every nothing job he does for Miscellaneous Affairs which turns out to be not quite so nothing.