Marcus Ryker is an agent with the CIA.
For morst of the time we follow him that is the case and as such he finds himself in some very sticky situations with a big variety of people wanting to do harm to him. Most of that is to keep him from learning the sorts of things they are up to or, since he is very good at his job and does learn those tightly kept secrets, to eliminate him to stop his acting on that intel. Luckily for us, he is also quite adept at staying alive.
When we first meet him, he is 21 years old, a rising senior in college in Colorado in May of 2001. Our introduction to him is a very violent one as he is racing home in response to a plea for help from his mother endangered by a very drunk and extremely violent husband, a recent stepfather Ryker never liked. The ensuing altercation will result in two firings up close with a shotgun and Ryker's life will take a sudden turn. That turn continues a few months later after 9/11 as Ryker, along with many, many others, lined up to volunteer to head to Afghanistan. In Ryker's case, it will be as a Marine.
Over the passage of a few years, we will watch Ryker go from serving a couple of tours, resulting in some undesired but favorable publicity from one horrifying firefight, to returning home to marry his long-term girlfriend and changing careers more than once. A spell as a police officer will transition to the Secret Service and then, after some time, to the CIA.
And in the Agency, his star will both glow brighter as his impressive exploits will become known to the White House and dimmer for the same reason; many at Langley will resent that attention including the sitting Director.
The adventures of Ryker will concentrate, naturally, a lot of time on him but there will be a considerable amount on other people playing major roles in those events. Chief of those other individuals is the fascinating story of Oleg Stefanovich Kraskin, senior aide to and son-in-law of the Russian President Luganov. Kraskin's life path will be as fully described as Ryker's and the two will have many vital interactions.