Clark Mason is an agent with the Spy Fighters.
That very unofficial sounding name is the one given a group of operatives working for the American government. As said in the opening page of the first recorded adventure, the one introducing us to Clark Mason:
"Every crisis in American history has caused Americans to dig grimly into their resources of ingenuity and courage to produce a weapon that will preserve our democracy against all enemies! In this era, when all our political chips are down, the successful combatting of Soviet espionage means life and death to the forces of freedom! Little can be accomplished by arresting spies after they have done their damage! Enemy agents must be checked through counterespionage! The extent of their networks, their secret techniques, their plans for wreaking ruination thoughout the world requires not only detection, but prevention! For this perilous purpose the top brains of our land created a precedent-shattering counterespionage shock force... The Spy Fighters! And this is their story..."
When we first meet Mason, he is a detective sergeant of a large eastern city. As he puts it, "I like my job and my job likes me". Then he is called to his captain's office, introduced to a man who tells him that he is to head to Washington where then and only then he will be told the reason for the visit. Mason is worried that means being forced to work in some boring office where the poor saps toiling there are "as alike as two paper clips". The address he is given takes him to the Institute for Boll Weevil Research and his heart sinks even lower.
That, of course, was just the cover and soon Mason is in intense training to become one of the elite, covert agents working for the Spy Fighters. It is not revealed exactly to which higher organization the Spy Fighters are attached. They are shown be respond to requests for assistance from Army Intelligence but that does just shows they help not, not answer to, that organization. But the Spy Fighters have offices all over the world and Mason will be visiting most of them at one time or another. As Mason puts it in the second adventure, "a spy-fighter must be Tokyo one day, Tanganikya the next, and Toledo, Ohio, the next!"
Mason is a very good looking man who took to his training well and so became an accomplished agent who most definitely has an eye for the ladies and they for him. He also has a very good sense of humor and while he takes his job quite seriously, is not above a biting remark here and there, even at himself.
Helping Mason on many of the earlier mission before disappearing from print is the beautiful blonde agent Vicki Chase who can fight and shoot as well as Mason and can also fly a plane and who knows what else. She is quick with the quip and unafraid of trouble and is a very welcome partner. In one of her last known missions, when she and Mason are captured and he searched for a weapon, she pulls a gun and shoots their way out of trouble, chastising one guard, "Next time, buster, don't be so polite! Search a lady! I just didn't come along for the ride!"