Mark Fropp is an agent with the CIA.
That fact is important at times to the adventures we follow Fropp doing but not the main emphasis of his activities; that lies with his unalterable desire for revenge against the man who ordered the death of Fropp's mother back when he was 13. Each of the five recorded tales we are given of him are really just segments of that theme, each ending but inexorably pointing to the next.
Fropp is the son of two people whose marriage was one of convenience and enhancement; there was no real love between the two but there was no animosity either. His father, James, was a political animal who was rising quickly in the politics of Washington state. When we meet him he has recently won the office of Lieutenant Governor of that state. We learn immediately that his latest step up was, along with the Governor, through the requested hand of a rich and very powerful man named Zachary Wayne. These two ambitious politicos had conspired to use Wayne's prowess to get elected and then fully intended to betray him. Unfortunately, their perfidy was discovered and Wayne's paid assassin killed the Governor-elect and nearly killed Fropp senior. He did, though, unfortunately kill Fropp's mother in the process, leaving a stunned and grieving teenage son to help bury her.
And that is the crux of this series. Fropp overheard a discussion shortly after the killing in which his father aroused Fropp's suspicions and then performed a deep-dive into his father's papers, finding a diary outlining all that had happened and why. That is when Fropp inveigled his new bodyguard to teach him all the experienced man knew of fighting and survival. Fropp had a long term plan to get revenge on Wayne.
Fropp had joined the CIA even before finishing university and while he worked for them, he also continued his ultimate trajectory. We are taken along for the ride as he goes about getting justice for his late mother.