Hugh Marston, aka 'The Hit Man', is an agent with British Intelligence.
To the rest of the world, Marston is a partner in the highly successful stockbroking firm of Martson and Blake, situated in London, but with the willingness to travel anywhere in the world to meet with clients. This flexibility is designed specifically to give him ample reason to take off at a moment's notice when a new mission crops up. When in the office, thanks to his high intelligence and probably not a small part to the contacts his true bosses have, he is very successful.
We learn from a hintsheet provided to us that Marston was "educated at Eton and St. John's College, Cambridge" where he was "outstanding both academically and on the sports field". When he graduated it was with first class honors in Law, Politics, and Modern Studies.
His skills in athletic endeavors were pronounced, excelling at the Modern Pentathlon so much so that it was expected by him and all that he would be asked to be part of the next British Olympics team. It also meant that he would be noticed by scouts for British Intelligence and after they came to visit with an offer, the chance to compete went away.
After an extremely rigorous training session where he was deemed one of the best to have ever been recruited into the service, Marston was set up in his cover job and his new life as an assassin for the Crown began. He gets informed that there is a new mission for him by watching the ticker-tape (for those who remember what that was) on the lookout for the stock name 'CHARON'. Apparently the movement of the price and the ending price together make up some sort of code.
Marston has a pretty nifty set of gadgets he uses on the job, some maybe prepared for him but others he clearly devises and creates himself. These include such goodies as a back-firing gun (woe to those who use it), and an exploding canteen. Also at his disposal is a trick portable typewriter, the parts of which turn into a gun, fishing gear that turn into a bow and arrow, and two different items which shoot darts (one a megaphone which is a bit odd and the other being a tobacco pipe used as a blowgun).
When we meet him he has already been on the job for a number of years and has shown over and again just how deadly he can be.
After a number of recorded adventures, the depictions change a bit to the time when Marston has decided he has had enough and wants out. His superior agrees as long as he trains a half dozen to be as good as he, which he does. Then those six are sent, one at a time, to take Marston out since he knows too much to be allowed to walk free. Bad mistake all around, as Marston will demonstrate.