Kent intersperses the story of Martha and Thomas with a mini-thriller subplot, in which hired assassins are sent to New England under the orders of Charles II to find and capture or kill the regicides (those personally responsible for the death of Charles I, many of whom had crossed to the colonies). Unfortunately the assassin characters never quite get developed enough, so while this portion of the book had great potential, it ended up falling somewhat flat for me.
In general, as with Kent's last book, I quite liked the obvious research she'd put into the composition of the text (she moved some things around and fleshed out backstories, as you'd have to, but there's definitely some historical foundation here). If reading this book makes anyone more interested in the fascinating episode of the regicides in New England, it's done its job, as far as I'm concerned.