Tom Grant is an agent with an unnamed British Intelligence agency.
He works for a woman named Martha Cole, a "tiny woman who resembles a garden gnome, sans floppy hat and pointy shoes". Though we do not learn any name for the government organization she heads, we are told early on that "this agency is unique. We gather intelligence, we provide close personal protection, we protect the interests of this country and its visitors, VIP's, and political assets." And we are told, by Cole to Grant, that Grant is Cole's best operative.
Their relationship is a deep one that is almost like a family, complete with a mother who is at times proud of her offspring and at other times deeply concerned about him. In the case of Grant, considering the mess he has allowed himself to become when we join up with him, the concern is warranted. When we encounter Grant in the first full length adventure, it is under less than charming conditions as he awakens in a bedroom with the effects of the previous night's indulgences showing their unhappiness, he blurrily looks the room for signs of the woman he shared the night with had gone and Grant was pleased at that. [In the novella prequel showing us a particularly unpleasant time in Grant's life, the anonymous woman was not gone and to Grant's annoyance wanted another session in bed - he was enough of a gentleman to not disappoint her.]
Grant, we are shown in the prequel, is suffering from a deep personal loss by drowning himself in liquor and diverting his grief with any woman at the bar in need of company. We will watch him pull himself out of this pattern but it will take a bit of time.
It will also take Isabella Wirth, a fascinating woman who has her own set of issues to deal with. Wirth is, we are told initially, a computer expert for "one of Britain's most secretive intelligence agencies and she is less than thrilled to be told that she has been given a field assignment. Yes, she admits, she had received the mandatory instructions in fieldwork five years before but that was only because it has become policy for all employees "to be trained up". She is not a field operative and does not want to be. Unfortunately, her boss does not care. Or at least that is what her boss believes and so do we readers, for a moment. Mysterious woman, Ms. Wirth, made even more so when we discover that there is a whole other level to her and if ever there was someone who was not who she appeared to be, it would be Wirth.
Together they will make a fascinating team of sorts, sometime working together and sometimes not.