Arella is an agent with the Israeli Mossad. David Gay is an agent with the American NSA.
As you noticed, there are no last names given here for Arella - she undoubtedly has one but despite looking, I saw no mention.
The two agents from different intelligence agencies as well as different countries create an ad hoc partnership which blossums into something much more as they are pooled together by their respective departments to go up against a very nasty international terrorist organization known as the Black Ravens. The struggle against that group will comprise all the action that these two will be involved in during the recorded adventures; considering how widespread and dangerous Black Raven is, that one opponent is more than enough to challenge both experienced terrorist hunters. When we first encounter the two, both have been in their line of work for some time and had already acquired their own reputation.
Arella was born and raised on a farm in the Golan region of Israel. She had grown to love working the land like her farmer father and did not anticipate anything other than such a life. Then a helicopter landed on their property when she was in grade school, her mother greeted the visitors and then said goodbye to her daughter and husband, boarded the craft, and went away for good. Arella would learn that her mother had been a Mossad operative who had given that work up but then was pulled back in. Years later when her own life took an unexpected twist, Arella would note the irony in the fact that now she, too, was in that line of work.
David has that abandonment issue as well, having an idealic young childhood in the west until his "mother upped and left [leaving him] with the sickening reality of a mechanic and bipolar father who later married a woman whose blood relatives were natives of Hades". The existence he then endured until he was old enough to leave is something too unpleasant to mention here and one he tries hard not to recall.
Together they make a pretty good team and as the dangers of the pursuit of Black Ravens get worse, they find they are drawn to each other for other reasons as well.