Cal Shepard is an agent with the CIA.
He has been with that government agency for the past 16 years having been recruited straight out of college, which would make him at or around 38 years old.
He works for a fellow named Patterson and is considered by that man to be his very best agent. "Known only to a handful of peo9ple at Langley, Shepard was one of a small group of operators from the Special Activities Division who comprised an elite search-and-destroy (SD) unit with the sole forucs of hunting down other assassins". The training that the SD teams received was incredible with "a heavy emphasis on fieldcraft and advanced urban sniping and concealment to create the ultimate self-reliant hunter of men. In its first year in operations abroad, Shepard's SD unit racked up more confirmed kills than all of the other clandestine units combined within that same region".
When we first meet him, he has been temporarily reassigned to the position of liaison with a private tech company founded and run by a computer genius named Burke who was developing "a new threat-detection software called Perseus" and the relationship was a very close one "with Burke providing insights into the technological side of things that Shepard had been relying on for years overseas while the weathered field agent gave a glimpse into the methodologies of a master assassin-hunter".
In addition to the need for such a liaison, Patterson chose Shepard to be that man because Patterson recognized the signs of an agent who was headed into "troublesome terrain" from too many missions and the physical and mental trauma that came with them. A very bad shoulder wound from a firefight in Algeria sealed the deal. Shepard did not put up any argument as that meant being home with his beloved Cassie.
That woman is his wife, the love of his life, and the soon to be mother of their unborn little girl. What happens to them will be the basis for even more of the determined agent that Shepard becomes.