Kyle Achilles is an agent for the President.
Well, eventually he is. As the first novella opens he is a CIA operative, a man who as a member of the Special Operations Group is willing to head to a foreign country to do things considered quite illegal there and all without official government backing. If he got caught, he was disavowed and on his own so not getting nabbed became a high priority. He had been doing such missions for a couple of years and for the most part enjoyed them immensely. Achilles is decidedly an adrenaline junkie.
Which would explain his great love of rock-climbing. The thrill of heading up the face of a cliff using only his fingers and his toes and his nerve is something that he seems to live for and while this form of entertainment seems quite insane to me, to Achilles it is a fantastic way of challenging himself and forcing himself to stay at the top of his game or plummet who knows how many feet below. Free-soloing, as it is called, involves climbing with no ropes or safety equipment of any sort and no use of tools like pitons to act as a anchor should a mishap occur.
He had always loved adventure and pushing himself. As a boy he and his brother Colin constantly challenged each other and in the process made each other even better. As a college student, he excelled at school but did even better as an athlete, resulting in an invitation to participate in the biathlon at the Olympic Games. Then an injury brought an end to his skiing-and-shooting days and he moved to his other love, climbing. When he participated in a couple of events and set a record or two, it brought him to the attention of a CIA recruiter and when he was offered a job, he grabbed it.
For five years he risked his neck on a regular basis for the Agency until a mission came that made him rethink his priorities and he walked away from it. As one person put it, the next year was his graduation holiday postponed. He traveled around Europe and climbed many interesting obstacles and generally just considered what he wanted to do for the rest of his life.
Achilles knew he was smart. He had always been intelligent, despite his willingly climbing tall things. His father and his brother had both become doctors and worked in the pharmaceutical industry and he knew he could go that route if he chose to. Before he could decide, life intervened.