Alton Blackwell is an expert in Cryptology. Mallory Wilson Blackwell is an expert in Forensic Accounting.
When we first meet the man, he is a captain in the U.S. Army, leading a small Intelligence collection detachment in Kandahar. While he had already served there for some time and had shown himself to be an effective leader of the group, his time there comes to an end when an explosive device is left by an Al Qaeda double agent and Blackwell is severely injured in the explosion which also killed several of his men. The injury to his leg would result in a permanent limp and end his forward-station work, putting him in Command and Control back at headquarters.
It is there that he meets Mallory Wilson, a lieutenant in the Army working in Forensic Accounting. The two become friends and there that they will both suffer more injuries in an adventure that will lead to both leaving the military and going their separate ways.
The friendship will remain and the two will stay in touch. Alton Blackwell will put his exceptional cryptology skills to work at Kruptos Inc, "a tech company specializing in the encryption and security of electronic communications", where he will rise to a management position. Mallory Wilson will a career move to the FBI, doing essentially the same sort of investigations but "the perpetrators are generally smarter".
Alton Blackwell is described as good looking, slightly above average height, with a "lean, compact fitness" thanks to "an ongoing love of rec soccer". Mallory Wilson is said to be very attractive in her Army uniform and drop-dead gorgeous in civilian attire. Over time the two will find their friendship growing into love will marriage following.
The two will also see their careers change again, somewhat, as both will become connected to the NSA and together they will find whole new lives dealing in mysteries and suspense, taking on evil corporations, mad scientists, terrorists, and would-be world-savers.