Mel Hunter is an agent with the Bureau.
Exactly which "Bureau" this is remains unstated. The assumption is that it is the FBI based largely on the use of the term 'special agent'. Still, a few other government agencies have the word 'bureau' in their names and there is nothing to say that still more, especially highly secret ones, might just be called that by their employees.
The story of Hunter is told in a baker's dozen of adventures. The first one is begun with Hunter making several very important announcements, the first of which is, "You are about to see one of the most closely guarded secrets and one of the most fantastic series of events ever recorded in the annals of counter-espionage. This is my story; the story of Mel Hunter who lives in your world ... a World of Giants."
Hunter is unique among all the other operative working for the department for one astounding reason: he is six inches tall!
Hunter will go on to explain, "The Bureau guards many fantastic secrets, but none quite so fantastic as Mel Hunter, me. Following my escape from a nightmare behind the Iron Curtain six months, I watched along with 14 doctor and 17 scientists and saw myself shrink to the size of a six-inch ruler. The shrinking had stopped. The scientists are hoping; still working on my case. And I was still a special agent ... a kind of special special agent."
We will discover soon that Hunter had been an accomplished espionage agent who had been on a highly classified operation breaking into a top-secret missile launch facility behind the Iron Curtain. After a mishap at the base, Hunter was exposed to a new rocket fuel being used for the vehicle. A brief time later, back home, Hunter and others were stunned to watch him begin to rapidly shrink in size until he was but 6" tall.
What caused the shrinking was unknown. Why it stopped when it did was unknown. How long it would last was unknown.
What was known, or at least made obvious, was that Hunter was a) now in constant peril from an incredible number of previously innocuous events, such as a pencil falling near him which could crush him, and b) he was able to get into places without being noticed, making him a fantastic espionage weapon.
Add to that the fact that medical tests revealed some important facts. He now possessed "superhuman manual dexterity coupled with agility and reflexes many times faster than normal", likened as being "somewhere between a hummingbird and a mongoose". He would need those talents daily just to survive the outside world but when on a mission, they would be invaluable.
Along with Hunter on that fateful mission, though not close enough to the explosion to be affected like Hunter was, was his best friend, Bill Winters. Winters was the one who got his dazed and groggy colleague out of the place and to safety. It is now Winters who provides vital services to the miniature Hunter. Winters is for the most part a bodyguard to Hunter. He also is a sounding board and confidant. And he is the transportation mechanism by which Hunter is able to get to and from the office and out into the field to do his work as an agent.
Hunter travels mostly inside a specially constructed briefcase which Winters carries around with him, handcuffed to his wrist to ensure someone does not walk off with it. A small chair is bolted to the insides and Hunter straps himself in for his ride. Air holes allow breathing and some light to get in but otherwise it has to be a pretty claustrophobic situation.