Kirby Calloway is a software expert.
He had spent quite a few years serving in the United States Navy in its Intelligence division so one of his sub-fields of expertise is the use of computers in the collection and analysis of highly sensitive data gathered by classified means about people, organizations, and countries (friend and foe). As a result of this knowledge and the skills to parlay it into his now civilian employment, Calloway can be said to be quite well off and successful.
His membership in this compendium comes because he will, in the course of his normal business life, come across information dealing with international criminal activities keenly linked to foreign governments and that will put him and his family in great danger. As a result, Calloway will find going on the offense as his best defense will push him back into the intelligence world and he will soon be leading a team made up of CIA and FBI agents.
The series is known as 'The Calloways' because while Kirby Calloway is without doubt the lead character in these adventures, playing important parts are his two nearly grown teenage sons, Ethan (aged 18 and a rising senior in high school) and Morgan (one year younger and soon to be a junior). Neither of these two are trained operatives nor do they have a desire to become ones but they will find themselves deeply involved in the same matter that their father lands into and they will finish growing up very quickly.
Interestingly, the first book is primarily about the two sons and is told from the viewpoint of Ethan. The next three adventures focus more on Kirby and the sons move to the background but are never totally out of the picture. Entering that frame, though, will be FBI agent Ellen Cortez who will become deeply connected to, and eventually a part of, the Calloways.