Sierra Six

When he sees a ghost from the past—a terrorist leader who was taken out years ago during his very first mission as a junior member of a CIA action team—the Gray Man is not one to leave a job unfinished or a blood debt unpaid.
"It's been more than a decade since the Gray Man's first mission, but the trouble's just getting started in this latest entry in the #1 New York Times bestselling series. Before he was the Gray Man, Court Gentry was Sierra Six, the junior member of Zack Hightower's CIA Special Activities team, Golf Sierra, aka the Goon Squad. Court's skills were fearsome and undeniable. Too bad he wasn't also a team player. It took weeks of training and withering scrutiny to mold him into one, but the effort was worth it-on their first mission they took out a terrorist leader. The prize was invaluable; the cost was agonizing. Now, years have passed. The Gray Man is on a simple mission when he sees a ghost: the long-dead terrorist, though he's remarkably energetic for a dead man. A decade of time hasn't changed the Gray Man. Whatever the cost, he isn't one to leave a job unfinished or a blood debt unpaid"--
It's been years since the Gray Man's first mission, but the trouble's just getting started in the latest entry in the #1 New York Times bestselling series.Before he was the Gray Man, Court Gentry was Sierra Six, the junior member of a CIA action team. In their first mission they took out a terrorist leader, at a terrible price. Years have passed. The Gray Man is on a simple mission when he sees a ghost: the long-dead terrorist, but he's remarkably energetic for a dead man. A decade of time hasn't changed the Gray Man. He isn't one to leave a job unfinished or a blood debt unpaid.