Roger Lincoln is an agent with the State Department.
By agent, we mean that he is referred to as a Special Agent in some places, as an "S-Man" in other spots, and he definitely can be found by checking in with that organization. That is what a woman named Cynthia Blake did and that is how we first meet Lincoln.
Cynthia, as everyone calls her, a young, attractive, and intelligent woman who earned a good salary as a top fashion reporter for a major magazine, was on a train sitting next to a man named Jack Saunders who was carrying two packages. A terrible accident derailed the train and the man was mortally wounded. His dying words where "give p-packages to ... to ... Roger Lincoln ... W..Washington S.s.s." Being extremely conscientious, and more than a little adventurous, she undertook the difficult task of locating someone named "Roger Lincoln" in the nation's capital. Not knowing anything more about him, she decided to "start at the top and work my way down". To her, the top was the State Department, and soon enough to Roger Lincoln.
Cynthia asked of Lincoln "are you a government agent - or an undercover man of some sort?" to which he responds, "Why, no! I just sort of do this, that and the other thing - with a bit of travel thrown in." Being not only perceptive but also determined, she immediately countered with "Is that supposed to mean Yes or NO?" Lincoln dodges the question and invites her to dinner.
Back for a moment to the "S-Man", in the case of Lincoln the "S" definitely stands for "State" as he is identified on many occassions as being a representative of that cabinent department and by extension, the American government. His coyness in his answer to Cynthi'a question comes largely from his being a trouble-shooter (my term) who is sent anywhere in the world (and beyond) where there is trouble that could affect American interests.
In one mission he looks for a missing leading voice for democracy in a Latin American country. In another he is sent to find out why a trade agreement for a needed mineral has hit a snag in a Middle Eastern nation. When an American pilot is captured behind the Iron Curtain, it is Lincoln who is sent to calm the waters and get the man back safely. For a while, his sphere of operation even leaves this sphere we call home, first when a stolen space station is being offered for sale to the highest bidder with Russia being most interested, and then when other extraterrestrial problems find their way to this planet with trouble like slavery and drug addiction.
There is even a matter of a 300+ year old female space alien falling for Lincoln. While that 'romance' will not last, it is not hard to understand why she would be interested because Lincoln, a blond-haired attractive man likely in his mid-to-late 30s, is quite the ladies' man
Being told that he routinely went looking for trouble, Lincoln says , "Never do - I just walk down the street and it finds me!"
Talking to a woman who seems upset by the words of an older man, "Looks like the square is giving you the heebie-jeebies."