Charlie Dark is an agent with the CIA.
He has been one since, well, the beginning. He reminisces once briefly about his time with the OSS during World War II so he was there when it went away and the nascent Agency came into being. And he has stuck around and been successful for quite a few years. He has also become in the minds of many of those in charge, a relic.
Which is a strange concept because in the antiguity world, a relic is a prized possession, something of value from the past to be honored and desired. That is most definitely not the case with Charlie Dark. "Of value", absolutely because Dark consistently gets accomplishments when truly no one else could. "Honored and desired", most definitely NOT.
The chronicler of Dark's adventures puts it far better than I could when he says in the intro to the collection :
Charlie inhabits a violent world - the CIA - yet he is nonviolent; indeed, he’s inept with weapons and scorns them. ("Any fool can shoot people.") He is old and fat, in a genre that conventionally calls for sleek young heroes. He is thunderingly conceited, an amiable know-it-all, in a world that normally allows no room for arrogant prima donnas. He is clever and ratiocinative in a world best known for its blundering screw-ups. He is an iconoclast in an organization that demands conformity. He insists upon working alone, even though the "company" that employs him is one that prizes team spirit and effort. He is intuitive and resourceful in the midst of an organization peopled by dogged data-gathering computer types. He is rumpled in the world of the neat; he is humorous in the world of the witless; he has nerve but not nerves; and his relationship with his boss, whom he refuses to call his "superior,' is characterized by mutual hatred and contemptuous loathing, even though the two characters exist in symbiosis: neither can survive without the other.
He is also rather desperate. He really enjoys only two things: eating, and practicing his trade - the trade of international trouble-shooter and extinguisher of brush-fires; a trade at which he is - and knows he is - the best in the world. Charlie’s greatest fear is that he will be fired: forced into ignominious retirement. In order to avoid that inevitable fate, Charlie goes to ever-increasing lengths to prove his inimitable excellence and therefore his indispensability. As he grows ever older and fatter, Charlie must continuously extend the outrageousness of his stunning feats of accomplishment. He is a man under constant desperate challenge; beneath the corpulent surface of self-confidence I believe there is a man very near utter panic.
While the above does an incredible job explaining Dark, it does tend to paint a not-so-glowing picture of the man, which is an accurate one. But it does not, perhaps because the writer was being modest, something Charlie Dark would never be, convey how fascinatingly brilliant and impressive Dark can be when handed an impossible assignment and he carries it off.
The world in which Dark operates is controlled by one man - his boss, Myerson. Myerson could be described by many as odious. While no one in the recorded adventures likely ever use that term, the few times someone has the inclination to comment at all about him, terms pointing to odius are spoken. No one likes Myerson and Myerson never gives anyone a reason to. Dark most assuredly does not like Myerson and Myerson in return hates, loathes, despises, and denigrates Dark.
Unfortunately for both of them, and to the delight of those reading the adventures, they both need each other desperately. Myerson knows that without someone to pull off the occasional miracle, he would have been let go years before. It is to Myerson's department that impossible, no-way missions are sent, in many instances simply because no one else wants the likely blot on their record. It certainly is not because the powers like Myerson. Myerson's one saving "grace" is the fact that his people pull off miracles. And by the term "his people" I mean Charlie Dark.
For Dark's part, as much as he cannot stand to be in the same room with Myerson, for whom he has zero respect and liking, Dark is well aware of the sad fact that since he is so old and so fat and so not "one of the team" he would have been ousted years before, not through incompetence but because he did not fit in. The one and only person who had protected Dark from forced retirement is Myerson and that is only because Myerson so desperately needs Dark to help him keep his job.
Two men - at constant odds with each other - so much in need of the other.
And while this hate-but-need relationship goes on, Charlie Dark is given one impossible task after another and succeeds brilliantly.