Leonora Cavendish is an agent with Triple S.
That is the unofficial though constantly used designation for the British intelligence agency known as Special Security Service. It is an interesting department because its area of jurisdiction seems to lie between the Special Branch and the Security Service (MI5). It appears to occasionally dip its toes in foreign waters but largely swims locally.
Cavendish is a woman who wears several identities. Cavendish, of course, is one though she often goes by the simpler to use "Laura". As the latter she runs the Cavendish Agency which is a staffing company in London specializing in providing domestic help whether permanent or temporary. She explains how running such a business also helps with her Triple S operations by commenting that her company is "a genuine domestic staff agency too, of course, but you'd be surprised how many 'interesting' houses you can get into as a cleaner, or a cook or a nanny".
Another one of her 'lives' is that of Leonora Carr, a quite famous actress known for having done one outstanding movie which made much of the world sit up and take notice, and then largely pulled a Greta Garbo act and walked away from the glamour. She still puts in an appearance here or there as Carr, perhaps to keep from being totally forgotten that several years before she was considered one of the "greatest sex symbols", or, most likely, to keep that persona alive in case she needed it again.
Though she is and has been for some time a Triple S operative, she is not know to be so by anyone except the man who runs the operations. In fact, two of its very best agents who will work with her on the two recorded adventures we have of her did not know of her involvement with the bureau until it became necessary to reveal the information to them. As she explains to them, "the whole point of the way I operate is that I have as little visible connection with Triple S as possible."
Those two male operative play as big a role in the events as she does [but she remains, in my opinion, the key element].
The first is Stone. Stone is just Stone, no first name, except to his close friends. He is a very good looking man in a "hard, Nordic type" of way with pale blue, "diamond-hard" eyes and a stillness that reminds Leonora of the "repose of a coiled spring, balanced, alert; not restful".
The second is Nick Marriot, a very laid-back, very relaxed looking man, "tall, loose-limbed [man] with curly hair" worn longer than usual. He is more like to be seen wearing faded jeans and looking like he "could have walked out of any coffee bar or any building site".
These two have been partners for some time and work very well together. Both seem a tad annoyed at being put on what they initially think of as baby-sitting duty watching over Cavendish.
They both, of course, will fall in love with Cavendish but then again, once you get to know her, you would, too.
[Note, the great mystery expert, Al Hubin, lists these books as being 'Peter Stone' adventures. While I have a different take on the series, his opinion is always worthy of heeding.'