Cliff Cornwall is an agent with the F.B.I.
He is a highly specializing agent, making his mark in the constant battle against enemy agents and saboteurs. He is so good at it that he is seconded to Army Intelligence on more than one occasion and even when he is not actually assigned to them he continues to work on their behalf. His duties take him around the world but towards the end of his recorded cases, his area of operation moves to the Panama Canal and parts around there.
Very little is mentioned about his background or about his personal life. From his depiction it is possible to see that he is in his late 20s or early 30s and he is definitely in good physical shape, able and willing to leap into action and go up against great odds coming out on top each time. He only becomes a prisoner of his opponents, it would seem, when he wants to get at them more easily.
Besides his physical conditioning, we know that he is a red-head with slight curls. He is also clean-shaven. He is usually dressed in a suit and tie unless he is forced to take his shirt off, a not uncommon occurrence.
In several of the 17 adventures, Cornwall is assisted by a quite resourceful young woman he meets and who helps him in the first mission. Lys Vallerie is her name, a raven-haired beauty whose father had been a victim of the bad guys in the case. She is offered a chance to go to Washington with him at the end and she did so, apparently becoming an agent on her own. She would be named by him as his partner a few times but then disappeared from the pages (transferred?).
In the dozen-plus cases that Cornwall is in, he shows himself to be highly resourceful and dedicated and quite successful. He just did so in such a vanilla way that it is not surprising he did not stick around long.