Jake Harrigan is a security consultant.
In the case of Harrigan, that definitely does not begin to tell the story since the man wore many figurative hats.
When we first meet him, he is an assassin in the pay of the CIA. He is happily married to Nancy who thinks he is a consultant who has to travel a lot when in fact he gets a call from his handler and away he goes to some other part of the world to eliminate a designated threat to America and then back home until the next ring.
The first recorded adventure we have of his activities will see that change drastically and for the rest of the wild and varied cases we follow, he will be as described above, a security consultant but that will not begin to describe the sorts of trouble Harrigan and his new partner will encounter.
Prior to his days with the Agency, Harrigan, described now as "a tough-looking, Irish-American, dark-haired guy in his early 30's", was a Navy SEAL. His team was working a mission to South America as part of a major anti-drug operation. The death of a close friend in that action had soured his enjoyment of the excitement and the danger but after a short time, the CIA, in the form of a real winner named Jennings, came offering a job as a contract agent.
"At first consideration, being a controlled assassin for the CIA seemed exciting, certainly something he could easily handle with his experience." But after a time that started to weigh on him. Going after terrorist leaders, especially those associated with al Qaeda, was something he was proud to do but when the assignments moved to "targeting private citizens of countries that the U.S. was not even at war with" was not sitting well with him.
Life is going to change drastically for Harrigan and he will become partners with a very capable and skilled and determined young woman named Sarah Schaumberg who is an agent with the FBI when we first meet her and who has an uncle in Israel who happens to be the head of Mossad. She will immediately become a major part of Harrigan's life, first professionally then personally.
The two will quickly become the go-to people used by the American President to take on matters best left very quiet.