James Turner is an agent with the NIA.
That acronym stands for the National Intelligence Agency. The locale he reports to is in Altoona, PA, where "an underground bunker ... had been transformed from an old coal mine into the North American headquarters of the preeminent counterintelligence agency in the world". Running operations was Howard Castle who had run things with the NIA since its creation twenty years before. Under his direction "governments had been toppled and new ones installed in their place". Often the missions that Castle ordered were of his own determination but more often, they were matters that could be handled by other agencies but passed to the NIA when "they didn't want to get their hands dirty".
Castle had "recruited Turner ten years earlier, plucking him out of obscurity after he graduated from West Point. He had originally been slated to work in Military Intelligence, so it wasn't much of a stretch when Howard asked him to come work at NIA. Three years of intensive training followed before he ever sent Turner into the field. He quickly rose through the ranks and became the top agent just before he turned twenty-seven. Five years later, he was still their best option when it came to delicate operations. Lately, though ..."
Turner's specialty was elimination. He killed people that Castle pointed at, sometimes retrieving something they had that his boss felt was needed elsewhere and sometimes just removing the person from existence. He is most certainly not a heartless killing machine, hence his boss' growing concern. Turner admits "when he closed his eyes at night, he could see the expression of horror on the faces of every person he had ever killed. People always told him killing would get easier, but it never did."
Considering that he, when we first meet him, tells us that he had removed 57 people since he started at NIA and was sitting at a booth in a diner preparing to add the 58th name to the list, he had a lot of images in his head and more to come.