Ryan Kealey is an agent for the CIA.
At least he was for a few years just prior to the start of the series. As the books begin, he had quit the Agency and had taken a job as a lecturer for the University of Maine.
At 33 years of age when the series starts, Kealey had already accomplished a lot. He had graduated with a business degree and gone to get a Masters at Duke. He was made a 1st Lieutenant upon graduation and entered Special Forces training immediately. As a Green Beret, he rose in rank quickly while winning several prestigious medals including the DSC, Legion of Merit, and the Bronze Star with oak leaf clusters.
His career in the military seemed guaranteed. He made the rank of Major in eight years and was highly respected. Then an incident brought an end to that career and almost his life. A traitor inside his outfit had killed everyone else, thinking Kealey was dead. He wasn't. After months in the hospital, an incident related to this ambush prompted his being asked to resign. He did so and accepted an offer with the CIA.
Several years of field work was enough for Kealey who grew tired of the violence and decided a calmer, more peaceful life was needed. He quit the Agency. Using his degree and his experience, he got a teaching position in Maine, bought an old three-story house on the coast and spent his spare time fixing it up.
Kealey is fairly happy with his life as the first book begins. He has a peaceful job and a gorgeous girl friend and a comfortable nest egg. He can also feel the boredom set in. He knows it would not be long before he would go back. It would just need a good reason. He would get one.