The Gray Man is the first of many books featuring the eponymous gray man, a former CIA assassin turned paid-for assassin. That man, whose real name is later revealed in the novel to be Courtland Gentry, has few connections to the people around him. But one of the few connections that he has is to his former mentor, Sir Donald Fitzroy.
Despite being an exceptionally skilled operator, Fitzroy has been kidnapped by a man called Lloyd, a former CIA agent that was kicked out of the agency because of his psychopathic behavior. Now, Lloyd works for a French corporation called Laurent Group, which is trying to advance a deal involving a Nigerian oil scheme that will make its shareholders much wealthier. To that end, Lloyd kidnaps Fitzroy to get to Gentry, who he wants to kill to ensure the deal goes through.
Gentry, however, is more skilled than he looks and won't let Lloyd complete his diabolical plan. On the run because of an assassination gone wrong, Gentry returns to the real world and works hard to simultaneously stop Lloyd and rescue one of the few people he truly cares about in Fitzroy - who also runs Cheltenham Security Services, the outfit Gentry now works for.
Ultimately, Gentry is successful in stopping Lloyd and in stopping the business deal - but not before Gentry makes another friend in Fitzroy's nice, who helps him successfully complete his mission.
