Grantham 'Grant' Waldron is an agent with the American Secret Service.
There is some question as to whether this Secret Service is a euphemism for American Intelligence or actually means the then division of the Treasury Department. As the six adventures proceed there are numerous references to diplomatic tours and actions which would seem far outside the scope of the actual department's mandate but on the other hand, Waldron does possess identification (a badge, perhaps?) which affords him a good deal of respect and attention and obedience by local authorities.
We learn straight away that Waldron is a trained polyglot, especially in speaking Italian, which he does like a native thanks in part to having served for five years at the embassy at Rome, where he "as duty called him, had drifted between the diplomatic corps and the powerful Secret Service arm of his country's machinery of government". He is quite accustomed to making use of "his power as a United States diplomatic agent and secret investigator".
He is described as being "a young man with that touch of seriousness in face and bearing which gives hint of a fighting nature. His complexion was dark, his mouth and chin firm and his face clean shaven".
When Waldron is not out and about handling his assignments or engaging in his personally chosen investigations, he resides in a "comfortable bachelor suite close to Central Park". He is unmarried and has no apparent long term affections for any member of the fairer sex but he does have an eye for the ladies. He resides alone in his apartment except for his only servant, his valet named Joseph.
- said by an Italian prince in danger of being assassinated while brandishing a revolver, "I do not like the idea of the taking of human life, especially my life."