Alex Parker is an agent with the CIA.
That is not her real name. What is, I do not know and she isn't forthcoming about it and it is pretty much irrelevant. As she mentions to the Director at the beginning of the first recorded adventure, after he has commented that she has had "seventeen different aliases" in the just over ten years she has been with the Agency, "actually it's only sixteen. One is my real name", going on to say when asked which one was real, "to be honest it's been so long since I used it that I almost forget". Alex Parker is the name she is going under when we first meet her and she is "kind of partial" to it so she remains using in.
As she explains to Turner (more on him in a moment), she was raised in an orphanage. "One of the places they recruit from is troubled teens with no family. Nobody to miss them." She had just turned 17 when they came to call, almost ready to go out on her own and nothing planned for what that might be. "They identify certain criteria that they're looking for. Once they select you, you're put through a long, rigorous training process. They mold you into what they want you to be."
In her case it was to be a Ghost. At least that is what they called her. "They spent the next four years molding me into the agent that they wanted. They taught me new languages, how to blend in, how to disappear, how to survive, and ... how to kill. How to kill in every possible situation, with whatever is at your disposal. They turned me into a killing machine. Unquestioning of orders, mission after mission, never missing home because, well, you have no home to go back to."
For the next seven years up to the time we encounter her, she has over one hundred kills on her record and she is very, very tired of it. She is thinking seriously of chucking it all and finding something else to do with her life when, in that first adventure, she learns that her partner for the past couple of years of missions has gone missing. Went rogue. With that action on his part, her life will change drastically.
Which brings us to Turner, a man around her age that her missing partner had inveigled into helping him and someone she knew she might have to eliminate when she first meets him. She learns early one that such drastic action will not be necessary and as a short time passes, she also learns she is pleased he is not a target for she is falling hard for the civilian. He will become a very important part of her life for the rest of the series, as will fellow agent Cole.
Together the three make a pretty good team.