K.C. Stone is a finder.
First of all, the initials of K.C. are not his real ones. The true name is never mentioned. The K.C. comes from the days of his youth in an orphanage where he was always getting into fights and a friend tried to keep him out of them by telling him to "Keep Cool". He would need to say it so often that he just started abbreviating it to 'KC'. The admonition never seemed to work but the initials stuck.
Second is my term for his occupation, which is based on what he does - and does exceedingly well. Most people call him a mercenary or a gun for hire but that is not really what he is known for. By that I mean this former Marine Special Forces soldier does not sign on to fight in some other country for some other nation or organization nor does he take on protection duty in someone's security company. He makes his living finding missing things which makes him sound more like a private investigator but, of course, Stone being Stone, he has no license.
We first learn of Stone when an innocent 5-year-old girl named Dawn is kidnapped and her guardian, her aunt, despairs about her being recovered. A security guard working for her tells her 'I once heard about a guy who takes care of things like this." He adds, "He can find her." Then he warns, when she talks of meeting this man, "he's a really bad man." Stone will very shortly prove both statements the guard made about him true - he can find her and he is a really bad man.
He is also pretty well paid for his work, $50k for starting the hunt for Dawn, for example, and another $50k on delivery. He can command such a hefty price because he gets the job done. If what is need finding can be found, he is likely the one to do it. This is because he will do whatever it takes. Emphasis on 'whatever'.
His reasoning is simple. Someone knows the truth. That someone is invariably known by someone else, who is in turn known by yet another person, and so on. The key is to ask enough questions of people and to make sure they give truthful answers. Stone can be pretty persuasive at that because most people will be forthcoming when enough fingers are, well, hurt. Thus in the example just given, Stone will ask around until he finds that 'another person' who will, eventually, lead him to that 'someone else' who will, again eventually, tell him about that original 'someone'.
Stone has a great deal of patience. He has at times sat motionless for hours waiting until the person he wants to talk to is available, during which time "Mount Rushmore has moved more than Stone". When it is time to move, though, do not blink and do not get in his way. The former will mean you missed him and the latter will annoy him.
For quite some time after we meet Stone, he is as he is said to have been most of his life - somber, unsmiling, unfriendly. He is a man with no need of friends which is good because he has none. Then he will meet that 5-year-old Dawn and things will kind of change for the man.
Stone's presence in this compendium will come from the sort of situations that will arise from his finding Dawn. The situation involved in her abduction would be enough in itself, considering the two main suspects are Presidential Candidate and the current sitting Vice President. Matters after that will stay in the same field.