Jack and Max Stalwart are agents with the GPF.
That acronym stands for the Global Protection Force.
The GPF is a worldwide force of junior secret agents whose aim is to protect the world's people, places, and possessions. It was started in 1947 by a man named Ronald Barter, who wanted to stop criminals from harming things that mattered in the world. When Ronald died, under mysterious circumstances, his son Gerald took over. The GPF's main offices are located somewhere in the Arctic Circle.
When you read 'junior secret agents' it would not be unnatural to think those new in the espionage business. That is true here, of course, but in addition, we learn that the agents of the GPF, such as the hero of this series, Both Jack and Max Stalwart are juniors in life as well.
Max is twelve. Jack nine.
They are the sons of John and Corinne. John is an American aerospace engineer who recently headed up the Mars Mission Program. Corinne is originally British and now spends her extra time volunteering at Jacks' school as well as studying Asian art.
It is important to note here that while both Jack and Max are agents, John and Corinne, loving parents who want only the best for their boys, have no clue that their kids go out at night on secret missions.
The two boys are able to get to wherever their efforts are needed via The Magic Map. This "is a world map that hangs on every GPF agent's wall. Recently, it was upgraded from wood to a hi-tech, unbreakable glass. Once an agent places the country shape in the right spot, the map lights up and transports him or her to his or her mission. The agent returns precisely one minute after he or she left."
This series is really a continuation of the series of 14 adventures dealing with the younger Jack when he discovers that his brother is not really at a special boarding school in England but is in fact missing and had gone that way while working as an agent with the GPF. To get help finding the lost Max, Jack agrees to become an operative himself and was able to finally locate him in the final adventure.
In this series, the two boys continue to work for the GPF and check-in each evening to learn what exciting place they will go to and thrilling work they will be asked to do.