Paul Marcus is a cryptographer.
Paul Marcus grew up on a farm in Virginia. He was a gifted football player, as a young man he played for the University of Michigan. Academically, his high school college scores were extraordinary, especially in mathematics. He learned languages easily. His talents caught the eye of recruiters at the CIA where he worked for two years. Marcus, however, was more intrigued with breaking codes rather than catching spies, so he moved over to NSA. He broke an exceedingly difficult code that exposed some movements by al Qaeda."
What he discovered, and what he would later use in other fields, was that often a single symbol could mean an idea or a short message and his knack for finding these symbols and deciphering their meaning made him very popular.
When his young daughter was diagnosed with "heightened arterial fibrillation" Marcus quit NSA and joined a medical facility where he worked for three years until he "cracked a type of gene therapy that could be used to stabilize false electronic signals sent through the hearts of those suffering from a type of ventricular arrhythmia." He had found something that might save his daughter's life.
Unfortunately a horrible attack along the side of a road left his wife and daughter murdered and him nearly and two years later he still has not recovered and doubts he ever will. The fact that his code-cracking would prove highly useful gave him no satisfaction since he could not use it to save the one he wanted; the Nobel Prize for Medicine he was awarded was nothing he wanted to accept.
Marcus' presence in this compendium comes not from his previous work with the CIA or NSA but from the work he will be asked to do - new deciphering that he will be handed, along with a considerable number of people who would gladly kill him to stop his mind from solving these problems - starting with why Sir Isaac Newton may have mentioned him several hundred years ago and why the cypher he left with the note might change the world.