This is fourth in the series and events from the previous books are mentioned semi-awkwardly right up front—most likely to remind or inform those who don't know/remember. So feel free to skip as the author ensures you won't miss out and you pay the price for the semi-awkward exposition regardless.
This is one of those books that you have to give its premise. In this case, that gently-bred women are frequent targets of kidnappings and that at least some of them are hearty souls who not only foil dastardly plots but become famous "agents of the crown" while they do and that a network of these doughty women naturally springs up as they solve crimes and get each other out of jams. Seriously, lots and lots of dastardly doings and you kind of just have to roll with it. Indeed, we arrive in Scotland to find not just a rash of horse theft but a jarring number of missing constables that nobody seems at all curious about. Which leads to one of the more ludicrous exchanges where our heroine, Rachel, yearns for adventure only to be reminded that she has already survived a kidnapping and incurred the debt of His Majesty's Government and that she is currently fleeing London because she's being targeted by more kidnappers.
I stopped reading at about 15% despite kind of liking Rachel. At least she isn't shy and she's capable of seeking out her own entertainment even in the depths of Scotland. But I had a really hard time immersing in the story for a lot of little things that just added up to too much. It started with all the period violations (yes, beyond the premise). Class distinctions are ignored or referred to only to be dispensed with, Rachel's comportment is more than a little out of line with nobody batting an eye (even before you tackle that she has a young, male bodyguard who follows her around). I don't always care about period accuracy, though, if the story is good. And maybe this one is, but I couldn't get past the characters. Specifically, Rachel's mopey cousin and our "hero", Luke. We're supposed to find Mr. Mopey sympathetic because he lost the woman he loves but he came across as more melodramatic brooder than actual sufferer to me. Cheering/reforming/comforting him is obviously going to be a big part of the story and I'm just rolling my eyes.
Luke is the bigger problem, though. I mean, he's all wringing his hands about his horses disappearing but can't be bothered to care that nearly as many constables have gone missing as well. And he's all "well, this is kind of a backwater and they probably just wandered off." Srsly? Nice to see so much empathy there, my Lord. But I finally shut down when he deliberately lied to Rachel about his identity. Like he's a naughty ten year-old who doesn't want to be caught, uh, owning the place? Yeah, Rachel said she wants to avoid the owner and just wants to borrow some books (because he apparently has an awesome library), but lying about being the guy? Like that isn't literally the stupidest thing he could have done right then? Okay, he might have shot himself in the foot. Oh wait, that's exactly what he did! Hijinks!
Anyway, it all added up to enough that I'm done. I might have been able to ignore any one of the elements that bothered me. But together they tanked my interest in continuing.