Sarah Hill is an agent with the GSF.
What the letters GSF stand for is not, as far as I could find, explained. What the organization is, though, is only slightly better explained. It is the most covert spy agency in the world, one that operates beyond the reach of any government. It is rather large to be so hush-hush having agents in most major cities around the world. Controlled by an oversight board which ensures that its missions and its actions remain inside the guidelines set on its creation. We do learn after a while that the Director of the CIA is very familiar with the group and uses or nudges them on occasion but the rest of the CIA seems totally in the dark.
Mack Farr is the man running operations for the GSF, a 60-ish man with a bald head and a stern demeanor. It is his job to send his agents into harm's way and to live with their deaths. He is also the man who has to deal with Sarah Hill.
Hill is in her late 20s, standing 5'6" and weighing 125 lbs. She is in the peak of physical shape which is vital in her line of work because Hill loves the action but hates working with others. That means when things get tough, as they always do, she must get herself out of the jam. Her martial arts skills are exceptional as is her athleticism. So is her willingness to leap into extremely dangerous situations.
She does not rely solely on her hand-to-hand skills for she loves her Colt 1911's, packing two of them at all times. "When Sarah had gone through training, she had received the highest marks of anyone in the history of the GSF in marksmanship. She had shattered records that had stood since the agency’s birth. She was a gifted killer." Later we learn that "it was (her brother) Ben who had first taught her how to shoot. It was just a fad for him, but it turned into something more for her." When not in the field, she spends as much time on the shooting range as anywhere else.
Helping her survive is Bryce, a computer expert who stays at HQ and monitors her actions, speaking to her via a secure comm piece. He is for the most part a typical nerd who is shy around woman (except Hill) and collects action figures, never to be removed from their packaging, but he does handle the banter with Hill like an equal and despite their constant sniping at each other, there is definite caring. On every mission he is determined to keep her alive and after each assignment, she pushes him more to having a life.
Having a life is more than Hill can say for herself, though, as she lives for the action a bit too much and suffers personally for the lack of intimacy. This is not good for her. It is even worse for those who cross her.