Bessy goes to work at a Scottish estate where her mistress asks her to keep a journal to write her observations in. To the OCD grammar freaks, this might bug you because the entries are shown written in an uneducated hand. The great thing about this is, that as the book goes on, you see Bessy improve, in both her writing and her observations skills.
Set in 1863, this was a very good Victorian mystery. I didn't have the twist worked out until sometime into the story.