Sarah Black is an agent with MI6.
We are told quite a bit about her from the blurb of her first recorded adventure where we learn, "Sarah Black is young, naïve, inexperienced, and the latest recruit into the world of international espionage. Thrown into a world where nothing is as it seems, and no one can be trusted, Sarah must learn the rules of the game quickly, just to survive." What that does not say is that at our actual introduction, she tells Michael, the gray-haired mature man who has been grooming her to be an operative, that she has decided to not pursue a career in the intelligence field; she has come to feel the cloak and dagger world and the decisions that the line of work would force upon her would not be in keeping with the kind of person she feels she is.
Of course, at that meeting, the always devious and scheming Michael will have already placed on the table between them a folder which she knows in her heart will have something that will change her mind. And it does, although since it is a graphic photo of a decapitated man, it would not have been surprising if it sent her running away. Well, surprising for someone else, perhaps. Black's response to the gruesomeness was to ask for more information. Both she and Michael knew she was hooked.
Black is not taught the intricacies of spycraft. She is given a NOC and thrown into the thick of things in an area of the world she had read about but not known well. What Michael was thinking, and the man is well known by his operatives to never do anything without thinking it through twice, is puzzling to more than just Black.
She has her wits and her skill with languages and her earnestness. She also has a determination to not fail.