Callum came from a clan which had, for many generations, specialized in breeding and training monogs, to sell as pets, guard animals, farm animals, and sometimes police animals. Of course, various members of the clan could make entirely different careers for themselves, though the raising and selling of monogs was what made the clan moderately wealthy (if far from rich enough to be among the nobility). It was also what led the clan, upon the passing of the surname law in 904, to choose the name "Monogwrangle."
Callum himself had no interest in working with monogs; instead, he joined the local police department when he turned 20, in 889. His clan had provided the Tanq PD with several monogs over the years (and continued to do so after Callum joined), a business connection which to some degree helped facilitate his enrollment in the department. After two years as a patrolman, he was promoted to detective. Five years later, he became his district's deputy chief. In 899, when Intervil was being organized, Tanq's chief of police, Carson Fishmonger, selected Callum as Tanq's liaison in the organization. When Fishmonger retired in 909, the new chief, Quinn Darkstrider, saw no reason to replace Callum.
However, due to Callum's handling of the investigation of The Chaos in 912, Darkstrider fired him (as one of his final acts as chief of police). Since that time, Callum has used his share of his clan's wealth to become a financier, investing in various businesses (including the building of asylums in several villages, starting with the Royal Asylum in First Village, where he had spent a great deal of time over the years as an agent of InterVil).