Onyxx is a department in the National Security Agency.
It consists of several teams of six men each to fight the nation's enemies behind the scenes. To accomplish their missions, they sometimes need the assistance of women, preferably beautiful, trained operatives, which they obtain through an agent-for-hire organization called Euro-Quest.
The author chose to call her spy adventures the Spy Games series as it really combines two groups, separate entities that often work together.
As stated, Euro-Quest is a for-profit group out of Europe who specialize in training and hiring incredibly gorgeous women to act as femme fatales and these ladies are very, very good at what they do. They are capable of literally charming the pants off most any man and getting him to reveal more than just his underwear.
The main group, though, is Onyxx, a very covert branch of NSA. Its agents are thoroughly and totally male with manly names like Ash, Casmir, Sully, and Sly. Each of these men signed a contract to work for seven years and during that time to put their personal lives on hold.
As with other spy-and-romance combinations where the concept is that the man and women protagonists end up together at the end of the book, the idea of a follow-up book in which either is out with someone else quite destroys the romance angle. Therefore, each book is about a different couple and the only real series bond is the organization for which they work. Although in this case, the author has been kind enough to present a recurring bad guy
This bad guy is sometimes the star of the series as he is quite good at being bad and with a name like The Chameleon, it is obvious that he can really be anyone. What he is, though, is known as the Chameleon is the world's greatest assassin, so good that even when he is caught and put in prison, he seems to keep killing in the outside world.