David Brook and Valerie Koester are agents for Canadian Intelligence.
If there is an actual name for the agency they work for, I have not found it, therefore the generic 'Intelligence' is used here.
The time period in which the adventures take place is on or about 1980. The Soviet Union was still around and the Cold War was still going on.
Brook is a retired agent from Canada. Koester is a former British agent apparently now residing in Canada. It is interesting that both people are by no means close enough to 'normal' retirement age so the question as to why they had left their particular agencies is not mentioned. One explanation may come from the description used for both as being "nonconformists and authority-flouters" so perhaps their departures had seen someone holding the doors for them.
Both of these highly trained and experienced operatives will be brought back into service, first Brook and then, because he needed a partner he could trust, Koester. That trust came from the time before their retirement when they had worked together several times and had seen their relationship grow close and eventually intimate.
The department they return to is run overall by the man known as the General, a man not surprised by their tendency to act independently and to do things their own way and a man who turns a blind eye to the rebelliousness since he is confident of successful missions. Not so open to such actions is their immediate supervisor, a man named Graydon who likes things done by the book and without any sense of humor; he is therefore often disappointed.