David Sloane is an agent with the Central Security Agency.
He has been an agent in very good standing with this department of American Intelligence for some time as the two-book series begins, the last three out in the field working in gray areas where knowing who were the good guys and who were not was extremely difficult but not knowing would get you killed. He had come to rely only on his partner for those three years, a fellow agent named Rogers who had gone through the same rigorous training and who knew, like Sloane, that your partner was your most valuable weapon.
Both Sloane and Rogers had a lot in common even before they became partners and the best of friends. They were both runaways from homes that were never happy. Separately they had joined the Navy when they reached 18 because they each had no other real prospects except the military. They were both content there, surrounded by people who did not care about their pasts or lack thereof. Then the computers at the CSA, going through the files of active military personnel looking for viable candidates to become agents spit both of their names out.
They were recruited, put through the harshest training they had every imagined, taught every element of spycraft that the Agency possessed, and it possessed a lot. This included how to kill to keep from being killed and both men had in the few years they had been in the field had to do that killing several times. They did not like it but they did not hesitate.
Sloane was not his real last name, which was Pritchard, but when he joined the CSA, his previous life was largely erased and a new identity created, complete with a rank of Lieutenant in the Navy. Sloane did not really care about the name change as his life beforehand was not something he cared to think about. Having a new, fake identity was likely something his sense of humor would have enjoyed. Standing 6'2" with wavy dark hair, penetrating blue eyes, and an "almost boyish handsomeness", Sloane had an air about him as someone who enjoyed life.
At least he did as the first book opens, before Sloane's life takes a drastic change as a mole in the Agency, seeking to keep his identity hidden, strikes at both he and Rogers. Rogers is killed. Sloane is gravely injured. Staying alive becomes a challenge in itself but Sloane wants more. He want revenge.