Paul McGrath is a janitor.
Really. He is. Shows up for work at a courthouse in New York City, puts on his overalls, fills his cart with cleaning supplies, and heads to his assigned area and does what he expected to do. He sweeps, dusts, mops, wipes, refills containers. All the required duties of a janitor performed by a man who never does less than his best.
When he has completed his normal tasks, he then tends to hang around. He watches. He observes. He notices. And since he is a janitor, he is almost invisible, just part of the normal environment. A step up from walls and doors. Slightly below delivery people as far as being watched and observed and noticed himself. I mean, why would he be of interest to anyone? Floors need sweeping and mopping. He does it. End of story.
McGrath has come the custodial work just recently. In fact, in the first recorded adventure, he has not yet applied for the position, he is that new.
When we first meet him, he is in U.S. Army Intelligence. He is a field agent and has been for twenty years, from just after he finished school. His father was a successful businessman who had expected his son to join the company and eventually take it over. McGrath had other ideas, largely because adventurous son did not agree much with pacifist father. Strike 'much' and add 'any'.
But when we encounter McGrath, father has been murdered and the news reached the son quite late and the only suspect for the crime has had the key file against him gone missing somewhere in the huge courthouse and no one was really looking for it because there was always another case to handle. McGrath decided to do the looking himself. And he, too, failed because he was now a civilian with no power and no access.
And that is when he got the idea to become a janitor. Janitors have no power but they most definitely have access. Near total access and that wonderful cloak of invisibility mentioned before.
Now with the ability to go where he needed to and look where he wanted, McGrath also found that as he did the watching and observing I talked about, he noticed a whole lot of things, some of which annoyed him or interested him and because he now had plenty of time on his hands when not mopping floors, things that annoyed or interested him got his attention.
The attention of a man who over the past 20 years had learned well how to gather intelligence and to handle the system and to get things done anonymously because no one really notices the janitor.