The Bridge Club is exactly that - a loose association of average people meeting to play bridge.
Most of the members are average, as stated, but a quartet of them are a bit more. None of the other members know or would even suspect them of being anything other than what they claim but just shows how good the four are at keeping their "little secret" exactly that - secret.
The foursome have no real leader but of the four the one with the most experience going up against bad guys the likes of which the "club" members find themselves dealing with is Bill Doolin. Oddly enough, he is the newest member of the team and the one most likely to not want the others doing what they do. Unfortunately for him, the other three do not often heed his advice and, more frustratingly, he finds their services something he needs more than he would like.
Doolin is a retired police detective, one who worked more than his share of homicides as well as other vicious crimes. He did that for twenty years for the Franklin City, a fair-sized suburb of Memphis. Prior to that, though, he had a good career working for the CIA as a field operative, handling nasty situations all over world. Of some importance for things that would happen later, a fair amount of his time early on was in Laos during the Vietnam War.
He put in his twenty and retired in good standing from the Agency. By no means old enough to stop working, he changed professions and became a police officer, eventually working his way to the aforementioned detective position. As the first recorded adventure of the Bridge Club takes place, he is in his early 60s, still robust and happy to be active.
The other three members of the Bridge Club quartet are Joan McCarthy, Suzie Johnson, and George Parker. The first two have an interesting backstory that would have made them noteworthy even without Doolin.
McCarthy is a retired school teacher who was drafted into teaching programming back in the infancy of personal computers. Wanting to be a good instructor, she learned. And learned enough to get hooked. And then learned enough to become a hacker. And then learned enough to fall in with a group of like-minded hackers who did it not for monetary gain but for fun and sport. McCarthy, though, took it a slightly different direction, explained below.
Johnson was not born with that name, it was given her by Witness Protection when she entered the program. Before then she and her husband at the time had been involved with a very dangerous crime lord in Central America. When they turned against him to help the U.S. government take him down, he killed the husband but missed the woman before having to fake his own death and disappearing. Now she lives a quiet life under a new identity (well, a couple of them but that is a different story) with a lot of money sacked away.
Parker is the third member but he has no secret past or extracurricular activity going on. He is a very successful attorney who has largely retired and is involved with the other two because he has taken a liking to Johnson and the two now make an aging couple.
The different direction McCarthy took with her hacking involves Johnson and Parker. They are cyber-vigilantes. They find very bad people who have stolen lots of money from good people and have gotten away with it. They use their particular skills to exact their form of justice. McCarthy does the hacking to get into bank accounts and police records and whatever else is needed. Johnson uses her knowledge of accounting and money-laundering to find where the stolen wealth is and how to steal it back, secretly returning it to the victims. Parker uses his knowledge of the law to then help McCarthy frame the culprits for crimes they did not actually commit.
It makes for an interesting combination. Doolin is about as straight-laced as one can be but even he knows sometimes a rule needs to be bent a bit. The other three are prone to getting involved where legally they really should stay out. Together, they make for a heck of a team.