Dan Morgan is an agent with Zeta Division.
Before I get into what Zeta is, it is important to state that he actually joins Zeta in the series but since he spends most of his time with them, it is most accurate to link them together.
As the series begins, Morgan is an antique car dealer and a fairly successful one. He had been before that an agent with the CIA for several years and before that he had been with Special Forces for a handful of time and troubles.
But at the first book, he is moderately content being the businessman he decided to be when his wife, Jenny, learned that instead of business trips he had taken, he had actually gone on missions for the Agency risking his life and their future. Jenny wasn't just concerned about herself but also about their young daughter, Alex, and the idea that Morgan's likelihood of returning home from one of his "trips" was seldom a good one caused her no little anguish.
So Morgan had quit. Said goodbye to the few friends he had and to the excitement that he was a tad embarrassed to admit he loved. He started a normal life. Then after almost a decade, his old boss and sometime friend, Plante, rang the doorbell to tell him Cougar was dead.
In his time with the military, Dan Morgan and Peter Conley were two peas in a pod. They did not look alike or have the same backgrounds or the same desires but when it came to action and getting the job done, both were extremely reliable and worked incredibly well together. They were best friends, closer than brothers.
Morgan was codenamed Cobra for his quick strike abilities. Conley was Cougar because he could stalk just about anything just about anywhere. It is unlikely that they were really given these codenames for this reason but they worked and they stuck for many years and many missions.
Then Jenny's ultimatum and Morgan's putting priorities right and later the news that Cougar was dead and Morgan was back in.
This time, though, in meant a job offer from an enigmatic organization called Zeta Division. Morgan learned what Zeta was - a non-governmental organization doing lots of things around the world to keep the peace where governments seemed unable to succeed. Who they were, though, was a whole other matter and not even Morgan knew that. But he was trying.