Suzan Fitzroy, aka Lady S, is an agent for CATRIG.
That acronym stands for the secretive non-governmental organisation called the Centre for Anti-Terrorism Research and Intelligence Gathering. By secretive, we mean that virtually nobody has any real data on it other than it is operated by a group of retired intelligence officers of from the member nations of the European Union.
We learn almost immediately that Fitzroy is a very beautiful, highly intelligent, sophisticated young woman likely in her late 20s. She is the adopted daughter and key assistant to James Fitzroy, roving ambassador, special correspondent for the American Secretary of State in Europe. As we are told in one blurb, "Suzan is a clever, multilingual young woman, in full bloom and perfectly happy in the eyes of an attentive father". We are also allowed to know that she has a past that is far from the diplomatic stage she now publicly trods and one that helps explain why this urbane lady is willing to take considerable risks to keep that past from being exposed and hurting her adopted father.
While Fitzroy's official point of origin is said to be New Zealand (read the first adventure to learn why), in a flashback in the first recorded adventure, we learn of a far different beginning when we watch a young girl named Shania Rivkas, 13 years of age, eavesdropping on her frightened parents in a Soviet Union rapidly falling apart. Her father talks of the KGB being out to eliminate those who knew too much of the criminal activities they might be charged upon the collapse; his fear of being so removed coming true that night as armed guards break in and seek to arrest the family. Her mother dies getting her out and only a chance meeting with a young man in the rainy streets saved the youngster.
On the run with trained killers after them, the two start a life of crime to survive, one lasting nearly two years before circumstances separate them and Rivkas learns to how to become a particularly good second-story thief, especially at hotels. How she would meet and then later become close to the elder Fitzroy and his wife is especially fun to read. That will start yet another life for the young woman, one that she will be especially good at until her past catches up with her and she is pushed into working in the clandestine world as a 'side' job, going by the 'war name' of Lady S.