Kate Moore is an agent with the CIA.
Kate Moore is a homemaker with a husband and two small children, living in Paris where her husband, Dexter, has a quite well paying job for a major U.S. bank with offices throughout Europe as well.
For quite a while into the first recorded adventures, it is the latter that we learn about with Kate. We learn how she is living and working in D.C. though what she is doing as her occupation is not mentioned except that she has been doing it for a while, it takes her frequently away from home for short times, and she is tiring of it. Dexter is middle management (or so) with the bank. The two of them make decent money but their house is a repair-drain and the two kids are in private school so when Dexter gets an opportunity for a huge promotion by transferring to Luxembourg, it looked like a great time for Kate to become a stay-at-home mom when they become expats in the tiny European duchy.
It is only as time goes along that we start to get evidence that there is a whole lot more to Kate than she lets on; more to her than even her husband has dreamed. Kate, we discover, is very good at reinventing herself as the situation demands. This often requires coming up with reasonable lies and Kate has become very good at them. Case in point, the comment on one of her inventions: "Once Katherine had begun this lie, she knew she'd have to play along with it fully. That was the secret to maintaining lies: not trying to hide them. It had always been disturbingly easy to lie to her husband."
Unfortunately for Kate, it turns out that he was also capable of lieing to her.