John Marshall is an assassin for the CIA.
The facts on Marshall, who also uses the alias of Paul Chandler, are scant in quantity. He stands about 5'8 tall. He does not consider himself attractive and has commented that women do not find him particularly sexy, although he had several encounters to the contrary.
The most unique aspect of Marshall is that he is the only one-armed agent in the CIA. He lost his left hand, separated just above the wrist, when he was 18 (reason unknown). He normally has a hook attached in its place.
Marshall is a highly deadly eliminator of the nation's troubles. He is a good shot, a heckuva fighter, and an expert with knives. He is quite competent with martial arts, even if his trainer considers him too flabby. The lack of a left hand has made him compensate with an extremely strong right hand, possessing a grip that can shatter a Coke bottle.
There is one very odd aspect to the series. In an almost haphazard manner, the character remarks that since as John Marshall he is supposed to have been killed several years before, he usually goes by the name Paul Chandler. Now, most agents have a history to them but this bit of background is written as though the fact that Marshall was been 'killed' was already well known to the reader as though there were previous books about him. Research has not revealed any additional books so the matter remains a mystery.
Marshall works for Cramer. As the head of Department LR of the CIA, he runs a practically autonomous group that gets the jobs that nobody else can handle. He is hardly the image of a spy, however, standing barely 5'5 and weighing over 300 pounds. Nevertheless, he is a dedicated man and one quite good at running the organization.