While Point of Honour is labelled 'alternate history', to be honest there's not a great deal of difference between this and actual English history of the period - the main change is that George III has gone made much earlier and Queen Caroline is Regent, as well as the Prince of Wales actually marrying his Catholic first wife and being put out of the line of succession.
In this setting, we meet Sarah Tolerance, who ran off with her brother's fencing master to Europe and is thus a Fallen Woman. After his death, she has returned to London and established herself as an inquiry agent, while everyone else expected her to turn to whoring to make a living. This expectation probably isn't helped by the fact that, when we meet her, Sarah is living in a cottage in the gardens of her aunt's brothel, since her aunt is the only member of her family who will have anything to do with her.
The storyline essentially focusses around a task Sarah is set, the reclamation of a gift once given to a mistress of her client's father. This is undertaken against a backdrop of Whigs and Tories jockeying for power as Queen Caroline is very ill and not expected to survive, so both political parties are keen to put 'their' successor on the throne. Sarah's client is one of these politicians and, from the moment he's described, it's pretty clear she's going to end up having sex with him despite her already-dodgy reputation.
In the end, what decided me towards giving this 4 stars instead of 3 was how things work out and the amount of donkey work Sarah has to do in order to make this happen - by the end of the book, pretty much everyone involved has done something they later regret and/or which the law is going to punish them for. This includes Sarah's client, so I would assume he's not going to be cropping up as a recurrent love interest in the next book (Petty Treason), though I get the feeling his successor has already been lined up...