Jackson Guild is an investigator for the U.S. Senate.
More specifically he is the lead investigator for the Senate Foreign Relations Committee. He has been so for a few years but prior to that gig, he had been, in a previous life, a reporter during the Gulf War. He explains early in the first adventure that back during the First Gulf War, he had gotten a chance to interview members of Uday Hussein's paramilitary Fedayeen Saddam, if not the main man himself, when he was surprised to be taken on a raid with them, a late-night excursion that saw the Iraqis attack and kill four British marines. That soured him on journalism as a career.
Guild has, when we meet him, some "baggage" as one man called it. According to that fellow, Guild was a drunk and a liar. "You think you're a lady's man, dontcha? 'Jack the Zipper'. You're divorced. Your old lady left when you flaked out [over the event mentioned above]". While that man's statement was meant to put Guild in his place, Guild himself would agree completely with the assessment, stating later on that he "had a nearly unshakable partnership with whiskey for 20 years. It's not a habit; it's an affair. The relationship began when my psyche took a shot of guilt in 1991, during the first Gulf War. A head shot. It dropped my ego like sack, and I proceeded to lose my wife to another man, my car to the repo guy, and my job to a [expletive] ending conversation aimed at [his] editor."
For all that, though, Guild does make an very intelligent and productive investigator, a hold-over from his reporter training, and though he works officially for the Senate, he does mingle more than a little with people in the Intelligence community. While he may not have been issued a cloak and dagger, he knows where to borrow them when he needs to.
While his name is spelled like the forerunner to a union and seems like it should be pronounced "gild", according to him, it actually rhymes with "wild".