This can stand on its own, you don't have to read the others to know the characters really. As far as I can tell based on the prologue it would fit after Becoming Lady Lockwood and Lady Emma's Campaign but only because of the prologue. Other than that it is really just Anna's story. Slavery aspect was interesting, I found it easier to read than the war topic of Emma's story. Philip annoyed me greatly at the beginning of the story and I liked him by the end though the probability of an aristocrat falling for a servant seems a bit unlikely. It makes sense with the setting of Jamaica far from London but still. I also didn't like that they never addressed what the others felt upon finding Anna missing, if she was just assumed dead, and their reaction upon her being alive.
